21966720 has 128 divisors (see below), whose sum is σ = 74247840. Its totient is φ = 5505024.

The previous prime is 21966691. The next prime is 21966727. The reversal of 21966720 is 2766912.

It is a tau number, because it is divible by the number of its divisors (128).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21966727) 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, 32304 + ... + 32976.

Almost surely, 2^21966720 is an apocalyptic number.

21966720 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 21966720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37123920).

21966720 is an abundant number, since it is smaller than the sum of its proper divisors (52281120).

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

21966720 is a wasteful number, since it uses less digits than its factorization.

21966720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 712 (or 700 counting only the distinct ones).

The product of its (nonzero) digits is 9072, while the sum is 33.

The square root of 21966720 is about 4686.8667572270. The cubic root of 21966720 is about 280.0625710503.

The spelling of 21966720 in words is "twenty-one million, nine hundred sixty-six thousand, seven hundred twenty".