21930720 has 192 divisors, whose sum is σ = 80994816. Its totient is φ = 4884480.

The previous prime is 21930709. The next prime is 21930721. The reversal of 21930720 is 2703912.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21930721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 204907 + ... + 205013.

It is an arithmetic number, because the mean of its divisors is an integer number (421848).

Almost surely, 2^21930720 is an apocalyptic number.

21930720 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 21930720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (40497408).

21930720 is an abundant number, since it is smaller than the sum of its proper divisors (59064096).

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

21930720 is a wasteful number, since it uses less digits than its factorization.

21930720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 193 (or 185 counting only the distinct ones).

The product of its (nonzero) digits is 756, while the sum is 24.

The square root of 21930720 is about 4683.0246636122. The cubic root of 21930720 is about 279.9094945583.

The spelling of 21930720 in words is "twenty-one million, nine hundred thirty thousand, seven hundred twenty".