21408364806864 has 40 divisors (see below), whose sum is σ = 63205648478400. Its totient is φ = 6116675659008.

The previous prime is 21408364806791. The next prime is 21408364806877. The reversal of 21408364806864 is 46860846380412.

It is a happy number.

It is a junction number, because it is equal to n+sod(n) for n = 21408364806798 and 21408364806807.

It is a congruent number.

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, 31857685389 + ... + 31857686060.

It is an arithmetic number, because the mean of its divisors is an integer number (1580141211960).

Almost surely, 2^{21408364806864} is an apocalyptic number.

21408364806864 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21408364806864 is an abundant number, since it is smaller than the sum of its proper divisors (41797283671536).

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

21408364806864 is a wasteful number, since it uses less digits than its factorization.

21408364806864 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 63715371467 (or 63715371461 counting only the distinct ones).

The product of its (nonzero) digits is 42467328, while the sum is 60.

The spelling of 21408364806864 in words is "twenty-one trillion, four hundred eight billion, three hundred sixty-four million, eight hundred six thousand, eight hundred sixty-four".