656521 has 4 divisors (see below), whose sum is σ = 658944. Its totient is φ = 654100.

The previous prime is 656519. The next prime is 656527. The reversal of 656521 is 125656.

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 656521 - 2¹ = 656519 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (656527) 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, 745 + ... + 1366.

It is an arithmetic number, because the mean of its divisors is an integer number (164736).

2⁶⁵⁶⁵²¹ is an apocalyptic number.

It is an amenable number.

656521 is a deficient number, since it is larger than the sum of its proper divisors (2423).

656521 is a wasteful number, since it uses less digits than its factorization.

656521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2422.

The product of its digits is 1800, while the sum is 25.

The square root of 656521 is about 810.2598348678. The cubic root of 656521 is about 86.9126264216.

The spelling of 656521 in words is "six hundred fifty-six thousand, five hundred twenty-one".