21604825 has 24 divisors (see below), whose sum is σ = 29435616. Its totient is φ = 15600000.

The previous prime is 21604823. The next prime is 21604829. The reversal of 21604825 is 52840612.

It is not a de Polignac number, because 21604825 - 2¹ = 21604823 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21604793 and 21604802.

It is not an unprimeable number, because it can be changed into a prime (21604823) by changing a digit.

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, 68869 + ... + 69181.

It is an arithmetic number, because the mean of its divisors is an integer number (1226484).

Almost surely, 2^21604825 is an apocalyptic number.

21604825 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21604825 is a deficient number, since it is larger than the sum of its proper divisors (7830791).

21604825 is a wasteful number, since it uses less digits than its factorization.

21604825 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 585 (or 580 counting only the distinct ones).

The product of its (nonzero) digits is 3840, while the sum is 28.

The square root of 21604825 is about 4648.0990738150. The cubic root of 21604825 is about 278.5160652008.

The spelling of 21604825 in words is "twenty-one million, six hundred four thousand, eight hundred twenty-five".