21661630236 has 36 divisors (see below), whose sum is σ = 55173782664. Its totient is φ = 7165423200.

The previous prime is 21661630223. The next prime is 21661630247. The reversal of 21661630236 is 63203616612.

21661630236 is a `hidden beast` number, since 2 + 1 + 6 + 616 + 3 + 0 + 2 + 36 = 666.

It is a tau number, because it is divible by the number of its divisors (36).

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a self number, because there is not a number n which added to its sum of digits gives 21661630236.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2291895 + ... + 2301326.

It is an arithmetic number, because the mean of its divisors is an integer number (1532605074).

Almost surely, 2^21661630236 is an apocalyptic number.

It is an amenable number.

21661630236 is an abundant number, since it is smaller than the sum of its proper divisors (33512152428).

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

21661630236 is a wasteful number, since it uses less digits than its factorization.

21661630236 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4593362 (or 4593357 counting only the distinct ones).

The product of its (nonzero) digits is 46656, while the sum is 36.

The spelling of 21661630236 in words is "twenty-one billion, six hundred sixty-one million, six hundred thirty thousand, two hundred thirty-six".