21518365816 has 16 divisors (see below), whose sum is σ = 41285237400. Its totient is φ = 10508969184.

The previous prime is 21518365747. The next prime is 21518365867. The reversal of 21518365816 is 61856381512.

It is a congruent number.

It is an unprimeable number.

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 3 ways as a sum of consecutive naturals, for example, 31276351 + ... + 31277038.

Almost surely, 2^21518365816 is an apocalyptic number.

It is an amenable number.

21518365816 is a deficient number, since it is larger than the sum of its proper divisors (19766871584).

21518365816 is a wasteful number, since it uses less digits than its factorization.

21518365816 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 62553438 (or 62553434 counting only the distinct ones).

The product of its digits is 345600, while the sum is 46.

The spelling of 21518365816 in words is "twenty-one billion, five hundred eighteen million, three hundred sixty-five thousand, eight hundred sixteen".