251391055 has 4 divisors (see below), whose sum is σ = 301669272. Its totient is φ = 201112840.

The previous prime is 251391047. The next prime is 251391067. The reversal of 251391055 is 550193152.

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

It is not a de Polignac number, because 251391055 - 2³ = 251391047 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 25139101 + ... + 25139110.

It is an arithmetic number, because the mean of its divisors is an integer number (75417318).

Almost surely, 2^251391055 is an apocalyptic number.

251391055 is a deficient number, since it is larger than the sum of its proper divisors (50278217).

251391055 is an equidigital number, since it uses as much as digits as its factorization.

251391055 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 50278216.

The product of its (nonzero) digits is 6750, while the sum is 31.

The square root of 251391055 is about 15855.3163008500. The cubic root of 251391055 is about 631.1267775034.

The spelling of 251391055 in words is "two hundred fifty-one million, three hundred ninety-one thousand, fifty-five".