21645288 has 96 divisors (see below), whose sum is σ = 68103360. Its totient is φ = 6082560.

The previous prime is 21645287. The next prime is 21645307. The reversal of 21645288 is 88254612.

21645288 is a `hidden beast` number, since 2 + 1 + 645 + 2 + 8 + 8 = 666.

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is not an unprimeable number, because it can be changed into a prime (21645287) 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, 33448 + ... + 34088.

It is an arithmetic number, because the mean of its divisors is an integer number (709410).

Almost surely, 2^21645288 is an apocalyptic number.

21645288 is a gapful number since it is divisible by the number (28) 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 21645288, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34051680).

21645288 is an abundant number, since it is smaller than the sum of its proper divisors (46458072).

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

21645288 is a wasteful number, since it uses less digits than its factorization.

21645288 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 727 (or 720 counting only the distinct ones).

The product of its digits is 30720, while the sum is 36.

The square root of 21645288 is about 4652.4496773205. The cubic root of 21645288 is about 278.6898314369.

The spelling of 21645288 in words is "twenty-one million, six hundred forty-five thousand, two hundred eighty-eight".