21617981915 has 16 divisors (see below), whose sum is σ = 27471713760. Its totient is φ = 16274603520.

The previous prime is 21617981753. The next prime is 21617981927. The reversal of 21617981915 is 51918971612.

It is not a de Polignac number, because 21617981915 - 2⁸ = 21617981659 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 704156 + ... + 734214.

It is an arithmetic number, because the mean of its divisors is an integer number (1716982110).

Almost surely, 2^21617981915 is an apocalyptic number.

21617981915 is a deficient number, since it is larger than the sum of its proper divisors (5853731845).

21617981915 is a wasteful number, since it uses less digits than its factorization.

21617981915 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 38542.

The product of its digits is 272160, while the sum is 50.

The spelling of 21617981915 in words is "twenty-one billion, six hundred seventeen million, nine hundred eighty-one thousand, nine hundred fifteen".