21561216015 has 32 divisors (see below), whose sum is σ = 34976148480. Its totient is φ = 11340261504.

The previous prime is 21561216013. The next prime is 21561216031. The reversal of 21561216015 is 51061216512.

It is not a de Polignac number, because 21561216015 - 2¹ = 21561216013 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21561216013) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1028872 + ... + 1049618.

It is an arithmetic number, because the mean of its divisors is an integer number (1093004640).

Almost surely, 2^21561216015 is an apocalyptic number.

21561216015 is a deficient number, since it is larger than the sum of its proper divisors (13414932465).

21561216015 is a wasteful number, since it uses less digits than its factorization.

21561216015 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21711.

The product of its (nonzero) digits is 3600, while the sum is 30.

The spelling of 21561216015 in words is "twenty-one billion, five hundred sixty-one million, two hundred sixteen thousand, fifteen".