21397608 has 64 divisors (see below), whose sum is σ = 60220800. Its totient is φ = 7126704.

The previous prime is 21397603. The next prime is 21397609. The reversal of 21397608 is 80679312.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is not an unprimeable number, because it can be changed into a prime (21397601) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 16885 + ... + 18107.

It is an arithmetic number, because the mean of its divisors is an integer number (940950).

Almost surely, 2^21397608 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 21397608, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30110400).

21397608 is an abundant number, since it is smaller than the sum of its proper divisors (38823192).

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

21397608 is an equidigital number, since it uses as much as digits as its factorization.

21397608 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1250 (or 1228 counting only the distinct ones).

The product of its (nonzero) digits is 18144, while the sum is 36.

The square root of 21397608 is about 4625.7548573179. The cubic root of 21397608 is about 277.6227652573.

The spelling of 21397608 in words is "twenty-one million, three hundred ninety-seven thousand, six hundred eight".