21709328640 has 144 divisors (see below), whose sum is σ = 69462609216. Its totient is φ = 5778432000.

The previous prime is 21709328639. The next prime is 21709328651. The reversal of 21709328640 is 4682390712.

It is a hoax number, since the sum of its digits (42) coincides with the sum of the digits of its distinct prime factors.

It is a junction number, because it is equal to n+sod(n) for n = 21709328592 and 21709328601.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2187690 + ... + 2197590.

Almost surely, 2^21709328640 is an apocalyptic number.

21709328640 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 21709328640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34731304608).

21709328640 is an abundant number, since it is smaller than the sum of its proper divisors (47753280576).

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

21709328640 is an equidigital number, since it uses as much as digits as its factorization.

21709328640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10496 (or 10482 counting only the distinct ones).

The product of its (nonzero) digits is 145152, while the sum is 42.

The spelling of 21709328640 in words is "twenty-one billion, seven hundred nine million, three hundred twenty-eight thousand, six hundred forty".