21515915985 has 32 divisors (see below), whose sum is σ = 34964784000. Its totient is φ = 11296513536.

The previous prime is 21515915983. The next prime is 21515916001. The reversal of 21515915985 is 58951951512.

It is not a de Polignac number, because 21515915985 - 2¹ = 21515915983 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21515915983) 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, 270526 + ... + 340904.

It is an arithmetic number, because the mean of its divisors is an integer number (1092649500).

Almost surely, 2^21515915985 is an apocalyptic number.

It is an amenable number.

21515915985 is a deficient number, since it is larger than the sum of its proper divisors (13448868015).

21515915985 is a wasteful number, since it uses less digits than its factorization.

21515915985 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 70705.

The product of its digits is 810000, while the sum is 51.

The spelling of 21515915985 in words is "twenty-one billion, five hundred fifteen million, nine hundred fifteen thousand, nine hundred eighty-five".