21894404661 has 12 divisors (see below), whose sum is σ = 31775136640. Its totient is φ = 14527091880.

The previous prime is 21894404657. The next prime is 21894404671. The reversal of 21894404661 is 16640449812.

21894404661 is a `hidden beast` number, since 2 + 189 + 4 + 4 + 0 + 466 + 1 = 666.

It is not a de Polignac number, because 21894404661 - 2² = 21894404657 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21894404611) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 5762821 + ... + 5766618.

Almost surely, 2^21894404661 is an apocalyptic number.

It is an amenable number.

21894404661 is a deficient number, since it is larger than the sum of its proper divisors (9880731979).

21894404661 is a wasteful number, since it uses less digits than its factorization.

21894404661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11529656 (or 11529653 counting only the distinct ones).

The product of its (nonzero) digits is 331776, while the sum is 45.

The spelling of 21894404661 in words is "twenty-one billion, eight hundred ninety-four million, four hundred four thousand, six hundred sixty-one".