21809615868 has 18 divisors (see below), whose sum is σ = 55129862424. Its totient is φ = 7269871944.

The previous prime is 21809615837. The next prime is 21809615879. The reversal of 21809615868 is 86851690812.

It is a happy number.

21809615868 is a `hidden beast` number, since 2 + 18 + 0 + 9 + 615 + 8 + 6 + 8 = 666.

It is a tau number, because it is divible by the number of its divisors (18).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 302911296 + ... + 302911367.

Almost surely, 2^21809615868 is an apocalyptic number.

It is an amenable number.

21809615868 is an abundant number, since it is smaller than the sum of its proper divisors (33320246556).

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

21809615868 is a wasteful number, since it uses less digits than its factorization.

21809615868 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 605822673 (or 605822668 counting only the distinct ones).

The product of its (nonzero) digits is 1658880, while the sum is 54.

The spelling of 21809615868 in words is "twenty-one billion, eight hundred nine million, six hundred fifteen thousand, eight hundred sixty-eight".