21197904025 has 27 divisors (see below), whose sum is σ = 27049387869. Its totient is φ = 16479024480.

The previous prime is 21197904011. The next prime is 21197904037. The reversal of 21197904025 is 52040979112.

It is a happy number.

The square root of 21197904025 is 145595.

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 2012329881 + 19185574144 = 44859^2 + 138512^2 .

It is not a de Polignac number, because 21197904025 - 2⁹ = 21197903513 is a prime.

It is a super-2 number, since 2×21197904025² (a number of 21 digits) contains 22 as substring.

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, 26934682 + ... + 26935468.

Almost surely, 2^21197904025 is an apocalyptic number.

21197904025 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21197904025 is the 145595-th square number.

21197904025 is the 72798-th centered octagonal number.

It is an amenable number.

21197904025 is a deficient number, since it is larger than the sum of its proper divisors (5851483844).

21197904025 is an frugal number, since it uses more digits than its factorization.

21197904025 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1658 (or 829 counting only the distinct ones).

The product of its (nonzero) digits is 45360, while the sum is 40.

The spelling of 21197904025 in words is "twenty-one billion, one hundred ninety-seven million, nine hundred four thousand, twenty-five".