21732720 has 80 divisors (see below), whose sum is σ = 68245632. Its totient is φ = 5720320.

The previous prime is 21732701. The next prime is 21732731. The reversal of 21732720 is 2723712.

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

It is a super-2 number, since 2×21732720² = 944622237196800, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 19375 + ... + 20465.

Almost surely, 2^21732720 is an apocalyptic number.

21732720 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 21732720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34122816).

21732720 is an abundant number, since it is smaller than the sum of its proper divisors (46512912).

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

21732720 is a wasteful number, since it uses less digits than its factorization.

21732720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1190 (or 1184 counting only the distinct ones).

The product of its (nonzero) digits is 1176, while the sum is 24.

The square root of 21732720 is about 4661.8365479712. The cubic root of 21732720 is about 279.0645654198.

The spelling of 21732720 in words is "twenty-one million, seven hundred thirty-two thousand, seven hundred twenty".