21653899904 has 64 divisors (see below), whose sum is σ = 53093725440. Its totient is φ = 8566373376.

The previous prime is 21653899871. The next prime is 21653899933. The reversal of 21653899904 is 40999835612.

It is a tau number, because it is divible by the number of its divisors (64).

It is a Harshad number since it is a multiple of its sum of digits (56).

It is a self number, because there is not a number n which added to its sum of digits gives 21653899904.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 917864 + ... + 941159.

It is an arithmetic number, because the mean of its divisors is an integer number (829589460).

Almost surely, 2^21653899904 is an apocalyptic number.

It is an amenable number.

21653899904 is an abundant number, since it is smaller than the sum of its proper divisors (31439825536).

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

21653899904 is a wasteful number, since it uses less digits than its factorization.

21653899904 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1859057 (or 1859045 counting only the distinct ones).

The product of its (nonzero) digits is 4199040, while the sum is 56.

The spelling of 21653899904 in words is "twenty-one billion, six hundred fifty-three million, eight hundred ninety-nine thousand, nine hundred four".