21331008 has 84 divisors (see below), whose sum is σ = 63299340. Its totient is φ = 6859776.

The previous prime is 21331001. The next prime is 21331021. The reversal of 21331008 is 80013312.

It can be written as a sum of positive squares in 2 ways, for example, as 12616704 + 8714304 = 3552^2 + 2952^2 .

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21331001) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 16066 + ... + 17342.

Almost surely, 2^21331008 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 21331008, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31649670).

21331008 is an abundant number, since it is smaller than the sum of its proper divisors (41968332).

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

21331008 is a wasteful number, since it uses less digits than its factorization.

21331008 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1324 (or 1311 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 18.

The square root of 21331008 is about 4618.5504219398. The cubic root of 21331008 is about 277.3344325236.

The spelling of 21331008 in words is "twenty-one million, three hundred thirty-one thousand, eight".