21425640625 has 21 divisors (see below), whose sum is σ = 26804598303. Its totient is φ = 17125875000.

The previous prime is 21425640623. The next prime is 21425640629. The reversal of 21425640625 is 52604652412.

It is a happy number.

The square root of 21425640625 is 146375.

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

It can be written as a sum of positive squares in 3 ways, for example, as 18770918049 + 2654722576 = 137007^2 + 51524^2 .

It is not a de Polignac number, because 21425640625 - 2¹ = 21425640623 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21425640623) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 20 ways as a sum of consecutive naturals, for example, 18296290 + ... + 18297460.

It is an arithmetic number, because the mean of its divisors is an integer number (1276409443).

Almost surely, 2^21425640625 is an apocalyptic number.

21425640625 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21425640625 is the 146375-th square number.

21425640625 is the 73188-th centered octagonal number.

It is an amenable number.

21425640625 is a deficient number, since it is larger than the sum of its proper divisors (5378957678).

21425640625 is an frugal number, since it uses more digits than its factorization.

21425640625 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2372 (or 1176 counting only the distinct ones).

The product of its (nonzero) digits is 115200, while the sum is 37.

The spelling of 21425640625 in words is "twenty-one billion, four hundred twenty-five million, six hundred forty thousand, six hundred twenty-five".