21122520021 has 6 divisors (see below), whose sum is σ = 30510306710. Its totient is φ = 14081680008.

The previous prime is 21122519981. The next prime is 21122520049. The reversal of 21122520021 is 12002522112.

21122520021 is a `hidden beast` number, since 2 + 1 + 122 + 520 + 0 + 21 = 666.

It can be written as a sum of positive squares in only one way, i.e., 11175449796 + 9947070225 = 105714^2 + 99735^2 .

It is not a de Polignac number, because 21122520021 - 2¹¹ = 21122517973 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21122519976 and 21122520003.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21122020021) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1173473326 + ... + 1173473343.

Almost surely, 2^21122520021 is an apocalyptic number.

It is an amenable number.

21122520021 is a deficient number, since it is larger than the sum of its proper divisors (9387786689).

21122520021 is a wasteful number, since it uses less digits than its factorization.

21122520021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2346946675 (or 2346946672 counting only the distinct ones).

The product of its (nonzero) digits is 160, while the sum is 18.

The spelling of 21122520021 in words is "twenty-one billion, one hundred twenty-two million, five hundred twenty thousand, twenty-one".