21115525 has 6 divisors (see below), whose sum is σ = 26183282. Its totient is φ = 16892400.

The previous prime is 21115511. The next prime is 21115559. The reversal of 21115525 is 52551112.

It is a happy number.

It can be written as a sum of positive squares in 3 ways, for example, as 5764801 + 15350724 = 2401^2 + 3918^2 .

It is not a de Polignac number, because 21115525 - 2⁹ = 21115013 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21115496 and 21115505.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 422286 + ... + 422335.

Almost surely, 2^21115525 is an apocalyptic number.

21115525 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21115525 is a deficient number, since it is larger than the sum of its proper divisors (5067757).

21115525 is an equidigital number, since it uses as much as digits as its factorization.

21115525 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 844631 (or 844626 counting only the distinct ones).

The product of its digits is 500, while the sum is 22.

The square root of 21115525 is about 4595.1632179935. The cubic root of 21115525 is about 276.3974050033.

Adding to 21115525 its reverse (52551112), we get a palindrome (73666637).

The spelling of 21115525 in words is "twenty-one million, one hundred fifteen thousand, five hundred twenty-five".