21404208 has 40 divisors (see below), whose sum is σ = 63194368. Its totient is φ = 6115392.

The previous prime is 21404183. The next prime is 21404213. The reversal of 21404208 is 80240412.

It is a Harshad number since it is a multiple of its sum of digits (21).

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, 31516 + ... + 32187.

Almost surely, 2^21404208 is an apocalyptic number.

21404208 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

21404208 is an abundant number, since it is smaller than the sum of its proper divisors (41790160).

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

21404208 is a wasteful number, since it uses less digits than its factorization.

21404208 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 63721 (or 63715 counting only the distinct ones).

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

The square root of 21404208 is about 4626.4681993936. The cubic root of 21404208 is about 277.6513061717.

It can be divided in two parts, 21404 and 208, that added together give a palindrome (21612).

The spelling of 21404208 in words is "twenty-one million, four hundred four thousand, two hundred eight".