21565718642 has 16 divisors (see below), whose sum is σ = 34863968832. Its totient is φ = 9945683280.

The previous prime is 21565718593. The next prime is 21565718651. The reversal of 21565718642 is 24681756512.

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, 287678 + ... + 354809.

It is an arithmetic number, because the mean of its divisors is an integer number (2178998052).

Almost surely, 2^21565718642 is an apocalyptic number.

21565718642 is a deficient number, since it is larger than the sum of its proper divisors (13298250190).

21565718642 is a wasteful number, since it uses less digits than its factorization.

21565718642 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 643793.

The product of its digits is 806400, while the sum is 47.

The spelling of 21565718642 in words is "twenty-one billion, five hundred sixty-five million, seven hundred eighteen thousand, six hundred forty-two".