21513725 has 24 divisors (see below), whose sum is σ = 27706560. Its totient is φ = 16560000.

The previous prime is 21513697. The next prime is 21513749. The reversal of 21513725 is 52731512.

It is not a de Polignac number, because 21513725 - 2⁸ = 21513469 is a prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21513694 and 21513703.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 142400 + ... + 142550.

It is an arithmetic number, because the mean of its divisors is an integer number (1154440).

Almost surely, 2^21513725 is an apocalyptic number.

21513725 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21513725 is a deficient number, since it is larger than the sum of its proper divisors (6192835).

21513725 is a wasteful number, since it uses less digits than its factorization.

21513725 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 341 (or 336 counting only the distinct ones).

The product of its digits is 2100, while the sum is 26.

The square root of 21513725 is about 4638.2890164370. The cubic root of 21513725 is about 278.1240453614.

The spelling of 21513725 in words is "twenty-one million, five hundred thirteen thousand, seven hundred twenty-five".