21372978025 has 27 divisors (see below), whose sum is σ = 30836812869. Its totient is φ = 14652247680.

The previous prime is 21372978019. The next prime is 21372978037. The reversal of 21372978025 is 52087927312.

The square root of 21372978025 is 146195.

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 2710139481 + 18662838544 = 52059^2 + 136612^2 .

It is not a de Polignac number, because 21372978025 - 2⁷ = 21372977897 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, 5114737 + ... + 5118913.

Almost surely, 2^21372978025 is an apocalyptic number.

21372978025 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21372978025 is the 146195-th square number.

21372978025 is the 73098-th centered octagonal number.

It is an amenable number.

21372978025 is a deficient number, since it is larger than the sum of its proper divisors (9463834844).

21372978025 is an frugal number, since it uses more digits than its factorization.

21372978025 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8378 (or 4189 counting only the distinct ones).

The product of its (nonzero) digits is 423360, while the sum is 46.

The spelling of 21372978025 in words is "twenty-one billion, three hundred seventy-two million, nine hundred seventy-eight thousand, twenty-five".