1851 has 4 divisors (see below), whose sum is σ = 2472. Its totient is φ = 1232.

The previous prime is 1847. The next prime is 1861. The reversal of 1851 is 1581.

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 not a de Polignac number, because 1851 - 2² = 1847 is a prime.

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.

It is not an unprimeable number, because it can be changed into a prime (1801) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 306 + ... + 311.

It is an arithmetic number, because the mean of its divisors is an integer number (618).

2¹⁸⁵¹ is an apocalyptic number.

1851 is a deficient number, since it is larger than the sum of its proper divisors (621).

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 product of its digits is 40, while the sum is 15.

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".