21656156261 has 8 divisors (see below), whose sum is σ = 22427539200. Its totient is φ = 20886414640.

The previous prime is 21656156251. The next prime is 21656156267. The reversal of 21656156261 is 16265165612.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21656156261 - 2³⁴ = 4476287077 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21656156267) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 383441 + ... + 436278.

It is an arithmetic number, because the mean of its divisors is an integer number (2803442400).

Almost surely, 2^21656156261 is an apocalyptic number.

It is an amenable number.

21656156261 is a deficient number, since it is larger than the sum of its proper divisors (771382939).

21656156261 is an equidigital number, since it uses as much as digits as its factorization.

21656156261 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 820659.

The product of its digits is 129600, while the sum is 41.

The spelling of 21656156261 in words is "twenty-one billion, six hundred fifty-six million, one hundred fifty-six thousand, two hundred sixty-one".