21897408 has 112 divisors (see below), whose sum is σ = 64633856. Its totient is φ = 6497280.

The previous prime is 21897397. The next prime is 21897431. The reversal of 21897408 is 80479812.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 77235 + ... + 77517.

It is an arithmetic number, because the mean of its divisors is an integer number (577088).

Almost surely, 2^21897408 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 21897408, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32316928).

21897408 is an abundant number, since it is smaller than the sum of its proper divisors (42736448).

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

21897408 is a wasteful number, since it uses less digits than its factorization.

21897408 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 342 (or 332 counting only the distinct ones).

The product of its (nonzero) digits is 32256, while the sum is 39.

The square root of 21897408 is about 4679.4666362738. The cubic root of 21897408 is about 279.7676984812.

The spelling of 21897408 in words is "twenty-one million, eight hundred ninety-seven thousand, four hundred eight".