21506878872 has 48 divisors (see below), whose sum is σ = 58255217280. Its totient is φ = 7168046400.

The previous prime is 21506878871. The next prime is 21506878879. The reversal of 21506878872 is 27887860512.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21506878871) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 783622 + ... + 810602.

It is an arithmetic number, because the mean of its divisors is an integer number (1213650360).

Almost surely, 2^21506878872 is an apocalyptic number.

It is an amenable number.

21506878872 is an abundant number, since it is smaller than the sum of its proper divisors (36748338408).

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

21506878872 is a wasteful number, since it uses less digits than its factorization.

21506878872 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 38064 (or 38057 counting only the distinct ones).

The product of its (nonzero) digits is 3010560, while the sum is 54.

The spelling of 21506878872 in words is "twenty-one billion, five hundred six million, eight hundred seventy-eight thousand, eight hundred seventy-two".