21366720 has 112 divisors (see below), whose sum is σ = 75407520. Its totient is φ = 5695488.

The previous prime is 21366713. The next prime is 21366721. The reversal of 21366720 is 2766312.

It is a happy number.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21366721) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 7404 + ... + 9876.

Almost surely, 2^21366720 is an apocalyptic number.

21366720 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 21366720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37703760).

21366720 is an abundant number, since it is smaller than the sum of its proper divisors (54040800).

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

21366720 is a wasteful number, since it uses less digits than its factorization.

21366720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2499 (or 2483 counting only the distinct ones).

The product of its (nonzero) digits is 3024, while the sum is 27.

The square root of 21366720 is about 4622.4149532468. The cubic root of 21366720 is about 277.4891157163.

The spelling of 21366720 in words is "twenty-one million, three hundred sixty-six thousand, seven hundred twenty".