21864720 has 160 divisors (see below), whose sum is σ = 75209472. Its totient is φ = 5226496.

The previous prime is 21864659. The next prime is 21864757. The reversal of 21864720 is 2746812.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 93724 + ... + 93956.

Almost surely, 2^21864720 is an apocalyptic number.

21864720 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 21864720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37604736).

21864720 is an abundant number, since it is smaller than the sum of its proper divisors (53344752).

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

21864720 is a wasteful number, since it uses less digits than its factorization.

21864720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 289 (or 283 counting only the distinct ones).

The product of its (nonzero) digits is 5376, while the sum is 30.

The square root of 21864720 is about 4675.9726260961. The cubic root of 21864720 is about 279.6284186660.

The spelling of 21864720 in words is "twenty-one million, eight hundred sixty-four thousand, seven hundred twenty".