Table:
|  | Number of Shares | Weighted Average Exercise Price ($) | Weighted Average Remaining Contractual Term (Years) | Aggregate Intrinsic Value of In-the- Money Options ($) |
| --- | --- | --- | --- | --- |
| Outstanding, December 31, 2018 | 4,864,836 | $17.76 |  |  |
| Exercised | -854,524 | 15.78 |  |  |
| Forfeited | -3,496 | 17.89 |  |  |
| Outstanding, December 31, 2019 | 4,006,816 | $18.18 | 3.71 | $78,949,941 |
| Exercisable, December 31, 2019 | 3,462,664 | $17.86 | 3.70 | $69,349,255 |
Paragraphs:
Stock Options
Stock options granted pursuant to the 2016 Incentive Plan are granted at an exercise price not less than the market value per share of the Company’s common stock on the date of grant. Under the 2016 Incentive Plan, the term of the outstanding options may not exceed ten years nor be less than one year. Vesting of options is determined by the compensation committee of the board and the administrator of the 2016 Incentive Plan and can vary based upon the individual award agreements. In addition, outstanding options do not have dividend equivalent rights associated with them under the 2016 Incentive Plan.
A summary of stock option activity is as follows:
The weighted average grant date fair value of stock options granted during the years ended December 31, 2018 and 2017, was $7.03 and $6.24, respectively. The Company did not grant stock options during the year ended December 31, 2019. The total intrinsic value of stock options exercised during the years ended December 31, 2019, 2018, and 2017, was $16.0 million, $15.8 million, and $13.4 million, respectively.
Question:
What is the change in the number of shares between outstanding and exercisable stock options as of December 31, 2019?
Answer: 4006816-3462664 = 544152