21089408 has 64 divisors (see below), whose sum is σ = 44457720. Its totient is φ = 9953280.

The previous prime is 21089407. The next prime is 21089437. The reversal of 21089408 is 80498012.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 17372224 + 3717184 = 4168^2 + 1928^2 .

It is a tau number, because it is divible by the number of its divisors (64).

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21089407) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 288860 + ... + 288932.

Almost surely, 2^21089408 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21089408, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22228860).

21089408 is an abundant number, since it is smaller than the sum of its proper divisors (23368312).

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

21089408 is an equidigital number, since it uses as much as digits as its factorization.

21089408 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 185 (or 173 counting only the distinct ones).

The product of its (nonzero) digits is 4608, while the sum is 32.

The square root of 21089408 is about 4592.3205463034. The cubic root of 21089408 is about 276.2834027981.

The spelling of 21089408 in words is "twenty-one million, eighty-nine thousand, four hundred eight".