21653280 has 144 divisors (see below), whose sum is σ = 80668224. Its totient is φ = 5245440.

The previous prime is 21653279. The next prime is 21653297. The reversal of 21653280 is 8235612.

21653280 is a `hidden beast` number, since 2 + 1 + 653 + 2 + 8 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (144).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 15157 + ... + 16523.

It is an arithmetic number, because the mean of its divisors is an integer number (560196).

Almost surely, 2^21653280 is an apocalyptic number.

21653280 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 21653280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (40334112).

21653280 is an abundant number, since it is smaller than the sum of its proper divisors (59014944).

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

21653280 is a wasteful number, since it uses less digits than its factorization.

21653280 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1399 (or 1388 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 27.

The square root of 21653280 is about 4653.3085004113. The cubic root of 21653280 is about 278.7241270469.

Adding to 21653280 its reverse (8235612), we get a palindrome (29888892).

It can be divided in two parts, 216532 and 80, that added together give a palindrome (216612).

The spelling of 21653280 in words is "twenty-one million, six hundred fifty-three thousand, two hundred eighty".