21726720 has 240 divisors, whose sum is σ = 80432352. Its totient is φ = 5406720.

The previous prime is 21726707. The next prime is 21726721. The reversal of 21726720 is 2762712.

It is a tau number, because it is divible by the number of its divisors (240).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21726721) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 529900 + ... + 529940.

Almost surely, 2^21726720 is an apocalyptic number.

21726720 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 21726720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (40216176).

21726720 is an abundant number, since it is smaller than the sum of its proper divisors (58705632).

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

21726720 is a wasteful number, since it uses less digits than its factorization.

21726720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 93 (or 74 counting only the distinct ones).

The product of its (nonzero) digits is 2352, while the sum is 27.

The square root of 21726720 is about 4661.1929803431. The cubic root of 21726720 is about 279.0388815431.

The spelling of 21726720 in words is "twenty-one million, seven hundred twenty-six thousand, seven hundred twenty".