21012563021 has 4 divisors (see below), whose sum is σ = 21020385792. Its totient is φ = 21004740252.

The previous prime is 21012562997. The next prime is 21012563041. The reversal of 21012563021 is 12036521012.

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 21012563021 - 2²⁶ = 20945454157 is a prime.

It is a super-2 number, since 2×21012563021² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21012563041) 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, 3907355 + ... + 3912728.

It is an arithmetic number, because the mean of its divisors is an integer number (5255096448).

Almost surely, 2^21012563021 is an apocalyptic number.

It is an amenable number.

21012563021 is a deficient number, since it is larger than the sum of its proper divisors (7822771).

21012563021 is an equidigital number, since it uses as much as digits as its factorization.

21012563021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7822770.

The product of its (nonzero) digits is 720, while the sum is 23.

The spelling of 21012563021 in words is "twenty-one billion, twelve million, five hundred sixty-three thousand, twenty-one".