21640964440225 has 27 divisors (see below), whose sum is σ = 29058202766763. Its totient is φ = 15980796599040.

The previous prime is 21640964440217. The next prime is 21640964440241. The reversal of 21640964440225 is 52204446904612.

The square root of 21640964440225 is 4651985.

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

It can be written as a sum of positive squares in 13 ways, for example, as 15479369590689 + 6161594849536 = 3934383^2 + 2482256^2 .

It is not a de Polignac number, because 21640964440225 - 2³ = 21640964440217 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 302343241 + ... + 302414809.

Almost surely, 2^{21640964440225} is an apocalyptic number.

21640964440225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21640964440225 is the 4651985-th square number.

21640964440225 is the 2325993-rd centered octagonal number.

It is an amenable number.

21640964440225 is a deficient number, since it is larger than the sum of its proper divisors (7417238326538).

21640964440225 is an frugal number, since it uses more digits than its factorization.

21640964440225 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 143174 (or 71587 counting only the distinct ones).

The product of its (nonzero) digits is 3317760, while the sum is 49.

The spelling of 21640964440225 in words is "twenty-one trillion, six hundred forty billion, nine hundred sixty-four million, four hundred forty thousand, two hundred twenty-five".