21661855796 has 12 divisors (see below), whose sum is σ = 43323711648. Its totient is φ = 9283652472.

The previous prime is 21661855783. The next prime is 21661855819. The reversal of 21661855796 is 69755816612.

21661855796 is an admirable number.

It is a hoax number, since the sum of its digits (56) coincides with the sum of the digits of its distinct prime factors.

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, 386818826 + ... + 386818881.

It is an arithmetic number, because the mean of its divisors is an integer number (3610309304).

Almost surely, 2^21661855796 is an apocalyptic number.

It is an amenable number.

21661855796 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

21661855796 is a wasteful number, since it uses less digits than its factorization.

21661855796 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 773637718 (or 773637716 counting only the distinct ones).

The product of its digits is 5443200, while the sum is 56.

The spelling of 21661855796 in words is "twenty-one billion, six hundred sixty-one million, eight hundred fifty-five thousand, seven hundred ninety-six".