21920640 has 192 divisors, whose sum is σ = 81628560. Its totient is φ = 4988928.

The previous prime is 21920621. The next prime is 21920651. The reversal of 21920640 is 4602912.

It is a tau number, because it is divible by the number of its divisors (192).

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 21920640.

It is a congruent number.

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, 93964 + ... + 94196.

Almost surely, 2^21920640 is an apocalyptic number.

21920640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21920640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (40814280).

21920640 is an abundant number, since it is smaller than the sum of its proper divisors (59707920).

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

21920640 is a wasteful number, since it uses less digits than its factorization.

21920640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 269 (or 250 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 24.

The square root of 21920640 is about 4681.9483124016. The cubic root of 21920640 is about 279.8666031242.

The spelling of 21920640 in words is "twenty-one million, nine hundred twenty thousand, six hundred forty".