21545664 has 224 divisors, whose sum is σ = 73737216. Its totient is φ = 5406720.

The previous prime is 21545663. The next prime is 21545683. The reversal of 21545664 is 46654512.

It is a tau number, because it is divible by the number of its divisors (224).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21545663) 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, 525484 + ... + 525524.

It is an arithmetic number, because the mean of its divisors is an integer number (329184).

Almost surely, 2^21545664 is an apocalyptic number.

21545664 is a gapful number since it is divisible by the number (24) 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 21545664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36868608).

21545664 is an abundant number, since it is smaller than the sum of its proper divisors (52191552).

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

21545664 is a wasteful number, since it uses less digits than its factorization.

21545664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 103 (or 93 counting only the distinct ones).

The product of its digits is 28800, while the sum is 33.

The square root of 21545664 is about 4641.7307117066. The cubic root of 21545664 is about 278.2616104373.

The spelling of 21545664 in words is "twenty-one million, five hundred forty-five thousand, six hundred sixty-four".