Table:
Jamo | Hangul Compatibility | Hangul Jamo Area | Hanyang Private Use | Halfwidth
ㅏ | U+314F | U+1161 | U+F807 | U+FFC2
ᅶ | — | U+1176 | U+F808 | —
ᅷ | — | U+1177 | U+F809 | —
ㅏㅡ | — | U+11A3 | U+F80A | —
ㅐ | U+3150 | U+1162 | U+F80B | U+FFC3
Jamo | Hangul Compatibility | Hangul Jamo Area | Hanyang Private Use | Halfwidth
ㅑ | U+3151 | U+1163 | U+F80C | U+FFC4
ᅸ | — | U+1178 | U+F80D | —
ᅹ | — | U+1179 | U+F80E | —
ㅑㅜ | — | U+11A4 | U+F80F | —
ㅒ | U+3152 | U+1164 | U+F810 | U+FFC5
Jamo | Hangul Compatibility | Hangul Jamo Area | Hanyang Private Use | Halfwidth
ㅓ | U+3153 | U+1165 | U+F811 | U+FFC6
ᅺ | — | U+117A | U+F812 | —
ᅻ | — | U+117B | U+F813 | —
ᅼ | — | U+117C | U+F814 | —
ㅔ | U+3154 | U+1166 | U+F815 | U+FFC7
Jamo | Hangul Compatibility | Hangul Jamo Area | Hanyang Private Use | Halfwidth
ㅕ | U+3155 | U+1167 | U+F816 | U+FFCA
ㅕㅑ | — | U+11A5 | U+F817 | —
ᅽ | — | U+117D | U+F818 | —
ᅾ | — | U+117E | U+F819 | —
ㅖ | U+3156 | U+1168 | U+F81A | U+FFCB
Jamo | Hangul Compatibility | Hangul Jamo Area | Hanyang Private Use | Halfwidth
ㅗ | U+3157 | U+1169 | U+F81B | U+FFCC
ㅘ | U+3158 | U+116A | U+F81C | U+FFCD
ㅙ | U+3159 | U+116B | U+F81D | U+FFCE
ㅗㅑ | — | U+11A6 | U+F81E | —
ㅗㅒ | — | U+11A7 | U+F81F | —
ᅿ | — | U+117F | U+F820 | —
ᆀ | — | U+1180 | U+F821 | —
ㅗㅕ | — | U+D7B0 | U+F822 | —
ᆁ | — | U+1181 | U+F823 | —
ᆂ | — | U+1182 | U+F824 | —
ㅗㅗㅣ | — | U+D7B1 | U+F825 | —
ᆃ | — | U+1183 | U+F826 | —
ㅚ | U+315A | U+116C | U+F827 | U+FFCF
Jamo | Hangul Compatibility | Hangul Jamo Area | Hanyang Private Use | Halfwidth
ㅛ | U+315B | U+116D | U+F828 | U+FFD2
ㅛㅏ | — | U+D7B2 | U+F829 | —
ㅛㅐ | — | U+D7B3 | U+F82A | —
ㆇ | U+3187 | U+1184 | U+F82B | —
ㆈ | U+3188 | U+1185 | U+F82C | —
ㅛㅓ | — | U+D7B4 | U+F82D | —
ᆆ | — | U+1186 | U+F82E | —
ᆇ | — | U+1187 | U+F82F | —
ㆉ | U+3189 | U+1188 | U+F830 | —
Jamo | Hangul Compatibility | Hangul Jamo Area | Hanyang Private Use | Halfwidth
ㅜ | U+315C | U+116E | U+F831 | U+FFD3
ᆉ | — | U+1189 | U+F832 | —
ᆊ | — | U+118A | U+F833 | —
ㅝ | U+315D | U+116F | U+F834 | U+FFD4
ᆋ | — | U+118B | U+F835 | —
ㅞ | U+315E | U+1170 | U+F836 | U+FFD5
ㅜㅕ | — | U+D7B5 | U+F837 | —
ᆌ | — | U+118C | U+F838 | —
ᆍ | — | U+118D | U+F839 | —
ㅟ | U+315F | U+1171 | U+F83A | U+FFD6
ㅜㅣㅣ | — | U+D7B6 | U+F83B | —
Jamo | Hangul Compatibility | Hangul Jamo Area | Hanyang Private Use | Halfwidth
ㅠ | U+3160 | U+1172 | U+F83C | U+FFD7
ᆎ | — | U+118E | U+F83D | —
ㅠㅐ | — | U+D7B7 | U+F83E | —
ᆏ | — | U+118F | U+F83F | —
ᆐ | — | U+1190 | U+F840 | —
ㆊ | U+318A | U+1191 | U+F841 | —
ㆋ | U+318B | U+1192 | U+F842 | —
ㅠㅗ | — | U+D7B8 | U+F843 | —
ᆓ | — | U+1193 | U+F844 | —
ㆌ | U+318C | U+1194 | U+F845 | —
Jamo | Hangul Compatibility | Hangul Jamo Area | Hanyang Private Use | Halfwidth
ㅡ | U+3161 | U+1173 | U+F846 | U+FFDA
ㅡㅏ | — | U+D7B9 | U+F847 | —
ㅡㅓ | — | U+D7BA | U+F848 | —
ㅡㅔ | — | U+D7BB | U+F849 | —
ㅡㅗ | — | U+D7BC | U+F84A | —
ᆕ | — | U+1195 | U+F84B | —
ᆖ | — | U+1196 | U+F84C | —
ㅢ | U+3162 | U+1174 | U+F84D | U+FFDB
ᆗ | — | U+1197 | U+F84E | —
Jamo | Hangul Compatibility | Hangul Jamo Area | Hanyang Private Use | Halfwidth
ㅣ | U+3163 | U+1175 | U+F84F | U+FFDC
ᆘ | — | U+1198 | U+F850 | —
ᆙ | — | U+1199 | U+F851 | —
ㅣㅑㅗ | — | U+D7BD | U+F852 | —
ㅣㅒ | — | U+D7BE | U+F853 | —
ㅣㅕ | — | U+D7BF | U+F854 | —
ㅣㅖ | — | U+D7C0 | U+F855 | —
ᆚ | — | U+119A | U+F856 | —
ㅣㅗㅣ | — | U+D7C1 | U+F857 | —
ㅣㅛ | — | U+D7C2 | U+F858 | —
ᆛ | — | U+119B | U+F859 | —
ㅣㅠ | — | U+D7C3 | U+F85A | —
ᆜ | — | U+119C | U+F85B | —
ㅣㅣ | — | U+D7C4 | U+F85C | —
ᆝ | — | U+119D | U+F85D | —
Jamo | Hangul Compatibility | Hangul Jamo Area | Hanyang Private Use | Halfwidth
ㆍ | U+318D | U+119E | U+F85E | —
ㆍㅏ | — | U+D7C5 | U+F85F | —
ᆟ | — | U+119F | U+F860 | —
ㆍㅔ | — | U+D7C6 | U+F861 | —
ᆠ | — | U+11A0 | U+F862 | —
ㆎ | U+318E | U+11A1 | U+F863 | —
ᆢ | — | U+11A2 | U+F864 | —

Question: which symbol is listed at the top of the jamo column?
Answer: ㅏ

Question: what is the number of halfwidth are there?
Answer: 21