251856 has 80 divisors (see below), whose sum is σ = 803520. Its totient is φ = 74880.

The previous prime is 251843. The next prime is 251857. The reversal of 251856 is 658152.

It is a Smith number, since the sum of its digits (27) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a nialpdrome in base 6.

It is a congruent number.

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

251856 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4726 + ... + 4778.

It is an arithmetic number, because the mean of its divisors is an integer number (10044).

2²⁵¹⁸⁵⁶ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 251856, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (401760).

251856 is an abundant number, since it is smaller than the sum of its proper divisors (551664).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

251856 is a wasteful number, since it uses less digits than its factorization.

251856 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 81 (or 69 counting only the distinct ones).

The product of its digits is 2400, while the sum is 27.

The square root of 251856 is about 501.8525679918. The cubic root of 251856 is about 63.1515625230.

It can be divided in two parts, 25 and 1856, that added together give a palindrome (1881).

The spelling of 251856 in words is "two hundred fifty-one thousand, eight hundred fifty-six".