656520639 has 4 divisors (see below), whose sum is σ = 875360856. Its totient is φ = 437680424.

The previous prime is 656520619. The next prime is 656520643. The reversal of 656520639 is 936025656.

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 656520639 - 2⁵ = 656520607 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 656520639.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (656520619) 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, 109420104 + ... + 109420109.

It is an arithmetic number, because the mean of its divisors is an integer number (218840214).

Almost surely, 2^656520639 is an apocalyptic number.

656520639 is a deficient number, since it is larger than the sum of its proper divisors (218840217).

656520639 is a wasteful number, since it uses less digits than its factorization.

656520639 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 218840216.

The product of its (nonzero) digits is 291600, while the sum is 42.

The square root of 656520639 is about 25622.6587027966. The cubic root of 656520639 is about 869.1261049146.

The spelling of 656520639 in words is "six hundred fifty-six million, five hundred twenty thousand, six hundred thirty-nine".