Question: What is the population of the city where the North Hertfordshire council is based?

Context paragraphs:
North Hertfordshire League: The North Hertfordshire League was a football competition based in England.  It had two divisions including the North Hertfordshire League Premier Division, which sat at level 13 of the English football league system and was a feeder to the Hertfordshire Senior County League.

Weston Hills, Baldock: Weston Hills is a 17 hectare Local Nature Reserve in Baldock in North Hertfordshire.  It is owned by Hertfordshire County Council and North Hertfordshire District Council (NHDC) and managed by NHDC.

Letchworth: Letchworth, officially Letchworth Garden City, is a town in Hertfordshire, England, with a population of 33,600.  It is a former civil parish.

Norton Common: Norton Common is a 25.7-hectare park and Local Nature Reserve in the centre of Letchworth Garden City, Hertfordshire.  It is owned and managed by North Hertfordshire District Council, and the declaring authority is Hertfordshire County Council.

North Hertfordshire: North Hertfordshire is a local government district in Hertfordshire, England.  Its council is based in Letchworth.

Barkway Chalk Pit: Barkway Chalk Pit is a small (0.3 hectare) nature reserve in Barkway in North Hertfordshire.  It was managed by the Herts and Middlesex Wildlife Trust (HMWT).  In February 2016 HMWT announced that three sites, Barkway Chalk Pit, Hill End Pit and Pryor's Wood, which HMWT managed on behalf of their owner, North Hertfordshire District Council, were to return to Council management as the Trust was no longer able to meet the cost.

North Hertfordshire District Council: North Hertfordshire District Council is the local authority for the North Hertfordshire non-metropolitan district of England, the United Kingdom.  North Hertfordshire covers the northern part of Hertfordshire, in the East of England region.  The Council's offices are in Letchworth, the largest settlement in the district.

Hill End Pit: Hill End Pit (also called Hill End Farm Pit or Hitch Wood Pit) is a 0.7 hectare a nature reserve on the site of a former chalk pit, in St Paul's Walden in North Hertfordshire.  It was formerly managed by the Herts and Middlesex Wildlife Trust (HMWT).  In February 2016 HMWT announced that three sites, Barkway Chalk Pit, Hill End Pit and Pryor's Wood, which HMWT managed on behalf of their owner, North Hertfordshire District Council, were to return to Council management as the Trust was no longer able to meet the cost.  It has the largest colony of Azeca goodalli snails in Hertfordshire.  Plants include viper's bugloss, cowslip and marjoram, there are butterflies such as common blue and gatekeeper, and many birds including woodpeckers.

Baldock Cemetery: Baldock Cemetery is the burial ground for the market town of Baldock in North Hertfordshire and the surrounding area.  It is maintained by North Hertfordshire District Council.

Wain Wood: Wain Wood is a 19.2 (47.4 acre) biological Site of Special Scientific Interest in Preston, North Hertfordshire.  The site was notified in 1986 under the Wildlife and Countryside Act 1981.  The local planning authority is North Hertfordshire District Council.

Supporting paragraphs: North Hertfordshire Letchworth
Answer: 33,600