21408204 has 24 divisors (see below), whose sum is σ = 50658048. Its totient is φ = 7035280.

The previous prime is 21408181. The next prime is 21408227. The reversal of 21408204 is 40280412.

It is an interprime number because it is at equal distance from previous prime (21408181) and next prime (21408227).

It is a super-2 number, since 2×21408204² = 916622397011232, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 11712 + ... + 13415.

It is an arithmetic number, because the mean of its divisors is an integer number (2110752).

Almost surely, 2^21408204 is an apocalyptic number.

It is an amenable number.

21408204 is an abundant number, since it is smaller than the sum of its proper divisors (29249844).

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

21408204 is a wasteful number, since it uses less digits than its factorization.

21408204 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25205 (or 25203 counting only the distinct ones).

The product of its (nonzero) digits is 512, while the sum is 21.

The square root of 21408204 is about 4626.9000421448. The cubic root of 21408204 is about 277.6685835466.

Adding to 21408204 its reverse (40280412), we get a palindrome (61688616).

It can be divided in two parts, 21408 and 204, that added together give a palindrome (21612).

The spelling of 21408204 in words is "twenty-one million, four hundred eight thousand, two hundred four".