21258720 has 384 divisors, whose sum is σ = 91929600. Its totient is φ = 4478976.

The previous prime is 21258691. The next prime is 21258733. The reversal of 21258720 is 2785212.

It is a super-3 number, since 3×21258720³ (a number of 23 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a zygodrome in base 3.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 574542 + ... + 574578.

It is an arithmetic number, because the mean of its divisors is an integer number (239400).

Almost surely, 2^21258720 is an apocalyptic number.

21258720 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 21258720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (45964800).

21258720 is an abundant number, since it is smaller than the sum of its proper divisors (70670880).

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

21258720 is a wasteful number, since it uses less digits than its factorization.

21258720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 87 (or 73 counting only the distinct ones).

The product of its (nonzero) digits is 2240, while the sum is 27.

The square root of 21258720 is about 4610.7179484328. The cubic root of 21258720 is about 277.0207945742.

The spelling of 21258720 in words is "twenty-one million, two hundred fifty-eight thousand, seven hundred twenty".