21520507051 has 4 divisors (see below), whose sum is σ = 21536725792. Its totient is φ = 21504288312.

The previous prime is 21520507033. The next prime is 21520507061. The reversal of 21520507051 is 15070502512.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21520507051 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21520507061) 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, 8107380 + ... + 8110033.

It is an arithmetic number, because the mean of its divisors is an integer number (5384181448).

Almost surely, 2^21520507051 is an apocalyptic number.

21520507051 is a deficient number, since it is larger than the sum of its proper divisors (16218741).

21520507051 is a wasteful number, since it uses less digits than its factorization.

21520507051 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16218740.

The product of its (nonzero) digits is 3500, while the sum is 28.

The spelling of 21520507051 in words is "twenty-one billion, five hundred twenty million, five hundred seven thousand, fifty-one".