21408304 has 20 divisors (see below), whose sum is σ = 43919064. Its totient is φ = 10074368.

The previous prime is 21408301. The next prime is 21408319. The reversal of 21408304 is 40380412.

It is not an unprimeable number, because it can be changed into a prime (21408301) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 39082 + ... + 39625.

Almost surely, 2^21408304 is an apocalyptic number.

It is an amenable number.

21408304 is an abundant number, since it is smaller than the sum of its proper divisors (22510760).

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

21408304 is a wasteful number, since it uses less digits than its factorization.

21408304 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 78732 (or 78726 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 22.

The square root of 21408304 is about 4626.9108485036. The cubic root of 21408304 is about 277.6690158858.

Adding to 21408304 its reverse (40380412), we get a palindrome (61788716).

It can be divided in two parts, 21408 and 304, that added together give a palindrome (21712).

The spelling of 21408304 in words is "twenty-one million, four hundred eight thousand, three hundred four".