21653760 has 72 divisors (see below), whose sum is σ = 69168960. Its totient is φ = 5773312.

The previous prime is 21653747. The next prime is 21653761. The reversal of 21653760 is 6735612.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a zygodrome in base 9.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21653761) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1021 + ... + 6659.

It is an arithmetic number, because the mean of its divisors is an integer number (960680).

Almost surely, 2^21653760 is an apocalyptic number.

21653760 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 21653760, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34584480).

21653760 is an abundant number, since it is smaller than the sum of its proper divisors (47515200).

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

21653760 is an equidigital number, since it uses as much as digits as its factorization.

21653760 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5663 (or 5649 counting only the distinct ones).

The product of its (nonzero) digits is 7560, while the sum is 30.

The square root of 21653760 is about 4653.3600763319. The cubic root of 21653760 is about 278.7261865746.

The spelling of 21653760 in words is "twenty-one million, six hundred fifty-three thousand, seven hundred sixty".