21716720 has 80 divisors (see below), whose sum is σ = 53032320. Its totient is φ = 8262912.

The previous prime is 21716713. The next prime is 21716729. The reversal of 21716720 is 2761712.

It is a tau number, because it is divible by the number of its divisors (80).

It is a self number, because there is not a number n which added to its sum of digits gives 21716720.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21716729) 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, 202907 + ... + 203013.

It is an arithmetic number, because the mean of its divisors is an integer number (662904).

Almost surely, 2^21716720 is an apocalyptic number.

21716720 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 21716720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26516160).

21716720 is an abundant number, since it is smaller than the sum of its proper divisors (31315600).

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

21716720 is a wasteful number, since it uses less digits than its factorization.

21716720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 222 (or 216 counting only the distinct ones).

The product of its (nonzero) digits is 1176, while the sum is 26.

The square root of 21716720 is about 4660.1201701244. The cubic root of 21716720 is about 278.9960645720.

The spelling of 21716720 in words is "twenty-one million, seven hundred sixteen thousand, seven hundred twenty".