21408336 has 30 divisors (see below), whose sum is σ = 59914010. Its totient is φ = 7136064.

The previous prime is 21408329. The next prime is 21408341. The reversal of 21408336 is 63380412.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 18974736 + 2433600 = 4356^2 + 1560^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 74191 + ... + 74478.

Almost surely, 2^21408336 is an apocalyptic number.

It is an amenable number.

21408336 is an abundant number, since it is smaller than the sum of its proper divisors (38505674).

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

21408336 is a wasteful number, since it uses less digits than its factorization.

21408336 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 148683 (or 148674 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 27.

The square root of 21408336 is about 4626.9143065330. The cubic root of 21408336 is about 277.6691542341.

Adding to 21408336 its reverse (63380412), we get a palindrome (84788748).

The spelling of 21408336 in words is "twenty-one million, four hundred eight thousand, three hundred thirty-six".