656213216021 has 32 divisors (see below), whose sum is σ = 768184788096. Its totient is φ = 553955584000.

The previous prime is 656213216011. The next prime is 656213216023. The reversal of 656213216021 is 120612312656.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-656213216021 is a prime.

It is a super-2 number, since 2×656213216021² (a number of 24 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (656213216023) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 4160561 + ... + 4315401.

It is an arithmetic number, because the mean of its divisors is an integer number (24005774628).

Almost surely, 2^656213216021 is an apocalyptic number.

It is an amenable number.

656213216021 is a deficient number, since it is larger than the sum of its proper divisors (111971572075).

656213216021 is a wasteful number, since it uses less digits than its factorization.

656213216021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 155173.

The product of its (nonzero) digits is 25920, while the sum is 35.

Adding to 656213216021 its reverse (120612312656), we get a palindrome (776825528677).

The spelling of 656213216021 in words is "six hundred fifty-six billion, two hundred thirteen million, two hundred sixteen thousand, twenty-one".