21456252640 has 48 divisors (see below), whose sum is σ = 52060421952. Its totient is φ = 8350539264.

The previous prime is 21456252589. The next prime is 21456252647. The reversal of 21456252640 is 4625265412.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (37).

It is a self number, because there is not a number n which added to its sum of digits gives 21456252640.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21456252647) 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, 1806264 + ... + 1818103.

It is an arithmetic number, because the mean of its divisors is an integer number (1084592124).

Almost surely, 2^21456252640 is an apocalyptic number.

21456252640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21456252640 is an abundant number, since it is smaller than the sum of its proper divisors (30604169312).

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

21456252640 is a wasteful number, since it uses less digits than its factorization.

21456252640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3624419 (or 3624411 counting only the distinct ones).

The product of its (nonzero) digits is 115200, while the sum is 37.

The spelling of 21456252640 in words is "twenty-one billion, four hundred fifty-six million, two hundred fifty-two thousand, six hundred forty".