21538425720 has 64 divisors (see below), whose sum is σ = 73846033920. Its totient is φ = 4923068544.

The previous prime is 21538425697. The next prime is 21538425743. The reversal of 21538425720 is 2752483512.

It is an interprime number because it is at equal distance from previous prime (21538425697) and next prime (21538425743).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 12819652 + ... + 12821331.

It is an arithmetic number, because the mean of its divisors is an integer number (1153844280).

Almost surely, 2^21538425720 is an apocalyptic number.

21538425720 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21538425720 is an abundant number, since it is smaller than the sum of its proper divisors (52307608200).

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

21538425720 is a wasteful number, since it uses less digits than its factorization.

21538425720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25641004 (or 25641000 counting only the distinct ones).

The product of its (nonzero) digits is 134400, while the sum is 39.

The spelling of 21538425720 in words is "twenty-one billion, five hundred thirty-eight million, four hundred twenty-five thousand, seven hundred twenty".