21653970 has 48 divisors (see below), whose sum is σ = 56287872. Its totient is φ = 5328960.

The previous prime is 21653959. The next prime is 21653987. The reversal of 21653970 is 7935612.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 2935 + ... + 7205.

It is an arithmetic number, because the mean of its divisors is an integer number (1172664).

Almost surely, 2^21653970 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21653970, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28143936).

21653970 is an abundant number, since it is smaller than the sum of its proper divisors (34633902).

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

21653970 is a wasteful number, since it uses less digits than its factorization.

21653970 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4307 (or 4294 counting only the distinct ones).

The product of its (nonzero) digits is 11340, while the sum is 33.

The square root of 21653970 is about 4653.3826406175. The cubic root of 21653970 is about 278.7270876084.

The spelling of 21653970 in words is "twenty-one million, six hundred fifty-three thousand, nine hundred seventy".