21501566015 has 4 divisors (see below), whose sum is σ = 25801879224. Its totient is φ = 17201252808.

The previous prime is 21501565991. The next prime is 21501566033. The reversal of 21501566015 is 51066510512.

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

It is a cyclic number.

It is not a de Polignac number, because 21501566015 - 2¹² = 21501561919 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2150156597 + ... + 2150156606.

It is an arithmetic number, because the mean of its divisors is an integer number (6450469806).

Almost surely, 2^21501566015 is an apocalyptic number.

21501566015 is a deficient number, since it is larger than the sum of its proper divisors (4300313209).

21501566015 is an equidigital number, since it uses as much as digits as its factorization.

21501566015 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4300313208.

The product of its (nonzero) digits is 9000, while the sum is 32.

The spelling of 21501566015 in words is "twenty-one billion, five hundred one million, five hundred sixty-six thousand, fifteen".