21697970139664 has 405 divisors, whose sum is σ = 54039722011821. Its totient is φ = 8411425102080.

The previous prime is 21697970139649. The next prime is 21697970139683. The reversal of 21697970139664 is 46693107979612.

The square root of 21697970139664 is 4658108.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 3209758896400 + 18488211243264 = 1791580^2 + 4299792^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21697970139593 and 21697970139602.

It is an unprimeable number.

It is a polite number, since it can be written in 80 ways as a sum of consecutive naturals, for example, 113601937809 + ... + 113601937999.

Almost surely, 2^{21697970139664} is an apocalyptic number.

21697970139664 is the 4658108-th square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21697970139664

21697970139664 is an abundant number, since it is smaller than the sum of its proper divisors (32341751872157).

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

21697970139664 is an equidigital number, since it uses as much as digits as its factorization.

21697970139664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 564 (or 280 counting only the distinct ones).

The product of its (nonzero) digits is 185177664, while the sum is 70.

The spelling of 21697970139664 in words is "twenty-one trillion, six hundred ninety-seven billion, nine hundred seventy million, one hundred thirty-nine thousand, six hundred sixty-four".