21115664664 has 16 divisors (see below), whose sum is σ = 52789161720. Its totient is φ = 7038554880.

The previous prime is 21115664627. The next prime is 21115664681. The reversal of 21115664664 is 46646651112.

It is a happy number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 439909657 + ... + 439909704.

Almost surely, 2^21115664664 is an apocalyptic number.

21115664664 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21115664664 is an abundant number, since it is smaller than the sum of its proper divisors (31673497056).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21115664664 is a wasteful number, since it uses less digits than its factorization.

21115664664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 879819370 (or 879819366 counting only the distinct ones).

The product of its digits is 207360, while the sum is 42.

The spelling of 21115664664 in words is "twenty-one billion, one hundred fifteen million, six hundred sixty-four thousand, six hundred sixty-four".