21013506621 has 32 divisors (see below), whose sum is σ = 32032765440. Its totient is φ = 13608504000.

The previous prime is 21013506617. The next prime is 21013506637. The reversal of 21013506621 is 12660531012.

21013506621 is a `hidden beast` number, since 2 + 1 + 0 + 1 + 35 + 0 + 6 + 621 = 666.

It is not a de Polignac number, because 21013506621 - 2² = 21013506617 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21013506601) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 71836 + ... + 217226.

It is an arithmetic number, because the mean of its divisors is an integer number (1001023920).

Almost surely, 2^21013506621 is an apocalyptic number.

It is an amenable number.

21013506621 is a deficient number, since it is larger than the sum of its proper divisors (11019258819).

21013506621 is a wasteful number, since it uses less digits than its factorization.

21013506621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 145554 (or 145548 counting only the distinct ones).

The product of its (nonzero) digits is 2160, while the sum is 27.

The spelling of 21013506621 in words is "twenty-one billion, thirteen million, five hundred six thousand, six hundred twenty-one".