21636608 has 40 divisors (see below), whose sum is σ = 49414992. Its totient is φ = 9271296.

The previous prime is 21636557. The next prime is 21636617. The reversal of 21636608 is 80663612.

It is a Harshad number since it is a multiple of its sum of digits (32).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 566 + ... + 6602.

Almost surely, 2^21636608 is an apocalyptic number.

21636608 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 21636608, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24707496).

21636608 is an abundant number, since it is smaller than the sum of its proper divisors (27778384).

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

21636608 is an frugal number, since it uses more digits than its factorization.

21636608 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6062 (or 6046 counting only the distinct ones).

The product of its (nonzero) digits is 10368, while the sum is 32.

The square root of 21636608 is about 4651.5167418811. The cubic root of 21636608 is about 278.6525738875.

The spelling of 21636608 in words is "twenty-one million, six hundred thirty-six thousand, six hundred eight".