21909872640 has 448 divisors, whose sum is σ = 74108828160. Its totient is φ = 5520752640.

The previous prime is 21909872599. The next prime is 21909872659. The reversal of 21909872640 is 4627890912.

It is a Harshad number since it is a multiple of its sum of digits (48).

It is a self number, because there is not a number n which added to its sum of digits gives 21909872640.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 277340121 + ... + 277340199.

Almost surely, 2^21909872640 is an apocalyptic number.

21909872640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21909872640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37054414080).

21909872640 is an abundant number, since it is smaller than the sum of its proper divisors (52198955520).

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

21909872640 is an equidigital number, since it uses as much as digits as its factorization.

21909872640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 211 (or 187 counting only the distinct ones).

The product of its (nonzero) digits is 435456, while the sum is 48.

The spelling of 21909872640 in words is "twenty-one billion, nine hundred nine million, eight hundred seventy-two thousand, six hundred forty".