It is a happy number.
1851 is an esthetic number in base 6, because in such base its adjacent digits differ by 1.
It is a semiprime because it is the product of two primes.
It is a cyclic number.
It is a D-number.
It is a nialpdrome in base 14.
It is a self number, because there is not a number n which added to its sum of digits gives 1851.
21851 is an apocalyptic number.
1851 is an equidigital number, since it uses as much as digits as its factorization.
1851 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 620.
The square root of 1851 is about 43.0232495286. The cubic root of 1851 is about 12.2782217572.
Adding to 1851 its product of digits (40), we get a triangular number (1891 = T61).
The spelling of 1851 in words is "one thousand, eight hundred fifty-one".