21656226251021 has 4 divisors (see below), whose sum is σ = 22402992673500. Its totient is φ = 20909459828544.

The previous prime is 21656226250979. The next prime is 21656226251071. The reversal of 21656226251021 is 12015262265612.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 3637644522121 + 18018581728900 = 1907261^2 + 4244830^2 .

It is a cyclic number.

It is not a de Polignac number, because 21656226251021 - 2¹⁰ = 21656226249997 is a prime.

It is a super-2 number, since 2×21656226251021² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21656226251021.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21656226251071) 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, 373383211196 + ... + 373383211253.

It is an arithmetic number, because the mean of its divisors is an integer number (5600748168375).

Almost surely, 2^{21656226251021} is an apocalyptic number.

It is an amenable number.

21656226251021 is a deficient number, since it is larger than the sum of its proper divisors (746766422479).

21656226251021 is an equidigital number, since it uses as much as digits as its factorization.

21656226251021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 746766422478.

The product of its (nonzero) digits is 172800, while the sum is 41.

The spelling of 21656226251021 in words is "twenty-one trillion, six hundred fifty-six billion, two hundred twenty-six million, two hundred fifty-one thousand, twenty-one".