21513521515 has 8 divisors (see below), whose sum is σ = 26649007488. Its totient is φ = 16655629440.

The previous prime is 21513521507. The next prime is 21513521527. The reversal of 21513521515 is 51512531512.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21513521515 - 2³ = 21513521507 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (31).

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 69398302 + ... + 69398611.

It is an arithmetic number, because the mean of its divisors is an integer number (3331125936).

Almost surely, 2^21513521515 is an apocalyptic number.

21513521515 is a deficient number, since it is larger than the sum of its proper divisors (5135485973).

21513521515 is a wasteful number, since it uses less digits than its factorization.

21513521515 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 138796949.

The product of its digits is 7500, while the sum is 31.

The spelling of 21513521515 in words is "twenty-one billion, five hundred thirteen million, five hundred twenty-one thousand, five hundred fifteen".