251555 has 4 divisors (see below), whose sum is σ = 301872. Its totient is φ = 201240.

The previous prime is 251543. The next prime is 251561. The reversal of 251555 is 555152.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 251555 - 2⁴ = 251539 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 251555.

It is an unprimeable 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 3 ways as a sum of consecutive naturals, for example, 25151 + ... + 25160.

It is an arithmetic number, because the mean of its divisors is an integer number (75468).

2²⁵¹⁵⁵⁵ is an apocalyptic number.

251555 is a deficient number, since it is larger than the sum of its proper divisors (50317).

251555 is an equidigital number, since it uses as much as digits as its factorization.

251555 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 50316.

The product of its digits is 1250, while the sum is 23.

The square root of 251555 is about 501.5525894660. The cubic root of 251555 is about 63.1263944403.

The spelling of 251555 in words is "two hundred fifty-one thousand, five hundred fifty-five".