21665502008 has 16 divisors (see below), whose sum is σ = 40942682880. Its totient is φ = 10747453248.

The previous prime is 21665502007. The next prime is 21665502017. The reversal of 21665502008 is 80020556612.

It is a Smith number, since the sum of its digits (35) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21665502007) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 10661141 + ... + 10663172.

It is an arithmetic number, because the mean of its divisors is an integer number (2558917680).

Almost surely, 2^21665502008 is an apocalyptic number.

It is an amenable number.

21665502008 is a deficient number, since it is larger than the sum of its proper divisors (19277180872).

21665502008 is a wasteful number, since it uses less digits than its factorization.

21665502008 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21324446 (or 21324442 counting only the distinct ones).

The product of its (nonzero) digits is 28800, while the sum is 35.

The spelling of 21665502008 in words is "twenty-one billion, six hundred sixty-five million, five hundred two thousand, eight".