21388173820225 has 27 divisors (see below), whose sum is σ = 27405378636681. Its totient is φ = 16558031215200.

The previous prime is 21388173820199. The next prime is 21388173820241. The reversal of 21388173820225 is 52202837188312.

It is a happy number.

The square root of 21388173820225 is 4624735.

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

It can be written as a sum of positive squares in 4 ways, for example, as 9347162779969 + 12041011040256 = 3057313^2 + 3470016^2 .

It is not a de Polignac number, because 21388173820225 - 2¹¹ = 21388173818177 is a prime.

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, 716819007 + ... + 716848843.

Almost surely, 2^{21388173820225} is an apocalyptic number.

21388173820225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21388173820225 is the 4624735-th square number.

21388173820225 is the 2312368-th centered octagonal number.

It is an amenable number.

21388173820225 is a deficient number, since it is larger than the sum of its proper divisors (6017204816456).

21388173820225 is an frugal number, since it uses more digits than its factorization.

21388173820225 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 59746 (or 29873 counting only the distinct ones).

The product of its (nonzero) digits is 2580480, while the sum is 52.

The spelling of 21388173820225 in words is "twenty-one trillion, three hundred eighty-eight billion, one hundred seventy-three million, eight hundred twenty thousand, two hundred twenty-five".