21315125 has 24 divisors (see below), whose sum is σ = 28833480. Its totient is φ = 15724800.

The previous prime is 21315109. The next prime is 21315137. The reversal of 21315125 is 52151312.

It is a happy number.

It can be written as a sum of positive squares in 12 ways, for example, as 21169201 + 145924 = 4601^2 + 382^2 .

It is not a de Polignac number, because 21315125 - 2⁴ = 21315109 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21315097 and 21315106.

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, 20621 + ... + 21629.

It is an arithmetic number, because the mean of its divisors is an integer number (1201395).

Almost surely, 2^21315125 is an apocalyptic number.

21315125 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21315125 is a deficient number, since it is larger than the sum of its proper divisors (7518355).

21315125 is a wasteful number, since it uses less digits than its factorization.

21315125 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1050 (or 1027 counting only the distinct ones).

The product of its digits is 300, while the sum is 20.

The square root of 21315125 is about 4616.8306228407. The cubic root of 21315125 is about 277.2655813229.

Adding to 21315125 its reverse (52151312), we get a palindrome (73466437).

The spelling of 21315125 in words is "twenty-one million, three hundred fifteen thousand, one hundred twenty-five".