21666066655620 has 48 divisors (see below), whose sum is σ = 60665564292480. Its totient is φ = 5777562759936.

The previous prime is 21666066655603. The next prime is 21666066655631. The reversal of 21666066655620 is 2655666066612.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4841344 + ... + 8171336.

It is an arithmetic number, because the mean of its divisors is an integer number (1263865922760).

Almost surely, 2^{21666066655620} is an apocalyptic number.

21666066655620 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21666066655620 is an abundant number, since it is smaller than the sum of its proper divisors (38999497636860).

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

21666066655620 is a wasteful number, since it uses less digits than its factorization.

21666066655620 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3438444 (or 3438442 counting only the distinct ones).

The product of its (nonzero) digits is 27993600, while the sum is 57.

The spelling of 21666066655620 in words is "twenty-one trillion, six hundred sixty-six billion, sixty-six million, six hundred fifty-five thousand, six hundred twenty".