21397936 has 40 divisors (see below), whose sum is σ = 48917504. Its totient is φ = 8873280.

The previous prime is 21397931. The next prime is 21397949. The reversal of 21397936 is 63979312.

It is not an unprimeable number, because it can be changed into a prime (21397931) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 391 + ... + 6553.

Almost surely, 2^21397936 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 21397936, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24458752).

21397936 is an abundant number, since it is smaller than the sum of its proper divisors (27519568).

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

21397936 is a wasteful number, since it uses less digits than its factorization.

21397936 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6209 (or 6203 counting only the distinct ones).

The product of its digits is 61236, while the sum is 40.

The square root of 21397936 is about 4625.7903108550. The cubic root of 21397936 is about 277.6241837928.

The spelling of 21397936 in words is "twenty-one million, three hundred ninety-seven thousand, nine hundred thirty-six".