21013000021 has 8 divisors (see below), whose sum is σ = 22630610744. Its totient is φ = 19395564480.

The previous prime is 21013000009. The next prime is 21013000033. The reversal of 21013000021 is 12000031012.

It is an interprime number because it is at equal distance from previous prime (21013000009) and next prime (21013000033).

It can be written as a sum of positive squares in 4 ways, for example, as 8120532996 + 12892467025 = 90114^2 + 113545^2 .

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 21013000021 - 2²⁵ = 20979445589 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21012999971 and 21013000007.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21013000081) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 313111 + ... + 374251.

It is an arithmetic number, because the mean of its divisors is an integer number (2828826343).

Almost surely, 2^21013000021 is an apocalyptic number.

It is an amenable number.

21013000021 is a deficient number, since it is larger than the sum of its proper divisors (1617610723).

21013000021 is a wasteful number, since it uses less digits than its factorization.

21013000021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 87591.

The product of its (nonzero) digits is 12, while the sum is 10.

Adding to 21013000021 its reverse (12000031012), we get a palindrome (33013031033).

The spelling of 21013000021 in words is "twenty-one billion, thirteen million, twenty-one", and thus it is an aban number and an uban number.