21708646400 has 432 divisors, whose sum is σ = 66425240700. Its totient is φ = 6991380480.

The previous prime is 21708646397. The next prime is 21708646409. The reversal of 21708646400 is 464680712.

It can be written as a sum of positive squares in 6 ways, for example, as 14577181696 + 7131464704 = 120736^2 + 84448^2 .

It is not an unprimeable number, because it can be changed into a prime (21708646409) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 42649346 + ... + 42649854.

Almost surely, 2^21708646400 is an apocalyptic number.

21708646400 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 21708646400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33212620350).

21708646400 is an abundant number, since it is smaller than the sum of its proper divisors (44716594300).

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

21708646400 is a wasteful number, since it uses less digits than its factorization.

21708646400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 572 (or 540 counting only the distinct ones).

The product of its (nonzero) digits is 64512, while the sum is 38.

The spelling of 21708646400 in words is "twenty-one billion, seven hundred eight million, six hundred forty-six thousand, four hundred".