21904825 has 6 divisors (see below), whose sum is σ = 27162014. Its totient is φ = 17523840.

The previous prime is 21904807. The next prime is 21904837. The reversal of 21904825 is 52840912.

It can be written as a sum of positive squares in 3 ways, for example, as 5992704 + 15912121 = 2448^2 + 3989^2 .

It is not a de Polignac number, because 21904825 - 2²¹ = 19807673 is a prime.

It is a Duffinian 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, 438072 + ... + 438121.

Almost surely, 2^21904825 is an apocalyptic number.

21904825 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21904825 is a deficient number, since it is larger than the sum of its proper divisors (5257189).

21904825 is an equidigital number, since it uses as much as digits as its factorization.

21904825 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 876203 (or 876198 counting only the distinct ones).

The product of its (nonzero) digits is 5760, while the sum is 31.

The square root of 21904825 is about 4680.2590740257. The cubic root of 21904825 is about 279.7992821703.

The spelling of 21904825 in words is "twenty-one million, nine hundred four thousand, eight hundred twenty-five".