21557172140 has 24 divisors (see below), whose sum is σ = 51737213472. Its totient is φ = 7391030400.

The previous prime is 21557172137. The next prime is 21557172149. The reversal of 21557172140 is 4127175512.

It is a Harshad number since it is a multiple of its sum of digits (35).

It is a self number, because there is not a number n which added to its sum of digits gives 21557172140.

It is not an unprimeable number, because it can be changed into a prime (21557172149) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 76989761 + ... + 76990040.

It is an arithmetic number, because the mean of its divisors is an integer number (2155717228).

Almost surely, 2^21557172140 is an apocalyptic number.

21557172140 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21557172140 is an abundant number, since it is smaller than the sum of its proper divisors (30180041332).

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

21557172140 is a wasteful number, since it uses less digits than its factorization.

21557172140 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 153979817 (or 153979815 counting only the distinct ones).

The product of its (nonzero) digits is 19600, while the sum is 35.

The spelling of 21557172140 in words is "twenty-one billion, five hundred fifty-seven million, one hundred seventy-two thousand, one hundred forty".