21666532550 has 48 divisors (see below), whose sum is σ = 44409084720. Its totient is φ = 7813895040.

The previous prime is 21666532549. The next prime is 21666532567. The reversal of 21666532550 is 5523566612.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21666532498 and 21666532507.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 359645 + ... + 415544.

It is an arithmetic number, because the mean of its divisors is an integer number (925189265).

Almost surely, 2^21666532550 is an apocalyptic number.

21666532550 is an abundant number, since it is smaller than the sum of its proper divisors (22742552170).

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

21666532550 is a wasteful number, since it uses less digits than its factorization.

21666532550 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 775257 (or 775252 counting only the distinct ones).

The product of its (nonzero) digits is 324000, while the sum is 41.

The spelling of 21666532550 in words is "twenty-one billion, six hundred sixty-six million, five hundred thirty-two thousand, five hundred fifty".