21315725 has 12 divisors (see below), whose sum is σ = 27343860. Its totient is φ = 16464000.

The previous prime is 21315719. The next prime is 21315761. The reversal of 21315725 is 52751312.

It can be written as a sum of positive squares in 6 ways, for example, as 2540836 + 18774889 = 1594^2 + 4333^2 .

It is not a de Polignac number, because 21315725 - 2⁴ = 21315709 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21315694 and 21315703.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 13976 + ... + 15425.

It is an arithmetic number, because the mean of its divisors is an integer number (2278655).

Almost surely, 2^21315725 is an apocalyptic number.

21315725 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21315725 is a deficient number, since it is larger than the sum of its proper divisors (6028135).

21315725 is a wasteful number, since it uses less digits than its factorization.

21315725 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 29440 (or 29435 counting only the distinct ones).

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

The square root of 21315725 is about 4616.8956020252. The cubic root of 21315725 is about 277.2681828838.

The spelling of 21315725 in words is "twenty-one million, three hundred fifteen thousand, seven hundred twenty-five".