251851 has 4 divisors (see below), whose sum is σ = 257752. Its totient is φ = 245952.

The previous prime is 251843. The next prime is 251857. The reversal of 251851 is 158152.

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 251851 - 2³ = 251843 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (251857) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2886 + ... + 2971.

It is an arithmetic number, because the mean of its divisors is an integer number (64438).

2²⁵¹⁸⁵¹ is an apocalyptic number.

251851 is a deficient number, since it is larger than the sum of its proper divisors (5901).

251851 is an equidigital number, since it uses as much as digits as its factorization.

251851 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5900.

The product of its digits is 400, while the sum is 22.

The square root of 251851 is about 501.8475864244. The cubic root of 251851 is about 63.1511446124.

The spelling of 251851 in words is "two hundred fifty-one thousand, eight hundred fifty-one".