251640617 has 4 divisors (see below), whose sum is σ = 264884880. Its totient is φ = 238396356.

The previous prime is 251640611. The next prime is 251640619. The reversal of 251640617 is 716046152.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 251640617 - 2²² = 247446313 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (251640611) 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, 6622103 + ... + 6622140.

It is an arithmetic number, because the mean of its divisors is an integer number (66221220).

Almost surely, 2^251640617 is an apocalyptic number.

It is an amenable number.

251640617 is a deficient number, since it is larger than the sum of its proper divisors (13244263).

251640617 is a wasteful number, since it uses less digits than its factorization.

251640617 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13244262.

The product of its (nonzero) digits is 10080, while the sum is 32.

The square root of 251640617 is about 15863.1843272402. The cubic root of 251640617 is about 631.3355533882.

Adding to 251640617 its reverse (716046152), we get a palindrome (967686769).

The spelling of 251640617 in words is "two hundred fifty-one million, six hundred forty thousand, six hundred seventeen".