21305760 has 192 divisors, whose sum is σ = 81430272. Its totient is φ = 4571136.

The previous prime is 21305741. The next prime is 21305761. The reversal of 21305760 is 6750312.

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

It is a self number, because there is not a number n which added to its sum of digits gives 21305760.

It is not an unprimeable number, because it can be changed into a prime (21305761) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 56934 + ... + 57306.

It is an arithmetic number, because the mean of its divisors is an integer number (424116).

Almost surely, 2^21305760 is an apocalyptic number.

21305760 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 21305760, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (40715136).

21305760 is an abundant number, since it is smaller than the sum of its proper divisors (60124512).

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

21305760 is a wasteful number, since it uses less digits than its factorization.

21305760 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 415 (or 407 counting only the distinct ones).

The product of its (nonzero) digits is 1260, while the sum is 24.

The square root of 21305760 is about 4615.8162875054. The cubic root of 21305760 is about 277.2249689637.

The spelling of 21305760 in words is "twenty-one million, three hundred five thousand, seven hundred sixty".