21391918140 has 48 divisors (see below), whose sum is σ = 59905792800. Its totient is φ = 5703709440.

The previous prime is 21391918129. The next prime is 21391918157. The reversal of 21391918140 is 4181919312.

It is a super-2 number, since 2×21391918140² (a number of 21 digits) contains 22 as substring.

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, 494086 + ... + 535634.

It is an arithmetic number, because the mean of its divisors is an integer number (1248037350).

Almost surely, 2^21391918140 is an apocalyptic number.

21391918140 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21391918140 is an abundant number, since it is smaller than the sum of its proper divisors (38513874660).

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

21391918140 is a wasteful number, since it uses less digits than its factorization.

21391918140 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 50142 (or 50140 counting only the distinct ones).

The product of its (nonzero) digits is 15552, while the sum is 39.

The spelling of 21391918140 in words is "twenty-one billion, three hundred ninety-one million, nine hundred eighteen thousand, one hundred forty".