21185604 has 96 divisors (see below), whose sum is σ = 63504000. Its totient is φ = 6036480.

The previous prime is 21185603. The next prime is 21185609. The reversal of 21185604 is 40658112.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (21185603) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 19672 + ... + 20720.

It is an arithmetic number, because the mean of its divisors is an integer number (661500).

Almost surely, 2^21185604 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21185604, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31752000).

21185604 is an abundant number, since it is smaller than the sum of its proper divisors (42318396).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21185604 is a wasteful number, since it uses less digits than its factorization.

21185604 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1090 (or 1082 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 27.

The square root of 21185604 is about 4602.7822021034. The cubic root of 21185604 is about 276.7028400630.

The spelling of 21185604 in words is "twenty-one million, one hundred eighty-five thousand, six hundred four".