21331440 has 240 divisors, whose sum is σ = 80432352. Its totient is φ = 5031936.

The previous prime is 21331399. The next prime is 21331451. The reversal of 21331440 is 4413312.

It is a tau number, because it is divible by the number of its divisors (240).

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 402454 + ... + 402506.

Almost surely, 2^21331440 is an apocalyptic number.

21331440 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 21331440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (40216176).

21331440 is an abundant number, since it is smaller than the sum of its proper divisors (59100912).

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

21331440 is a wasteful number, since it uses less digits than its factorization.

21331440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 128 (or 119 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 18.

The square root of 21331440 is about 4618.5971896237. The cubic root of 21331440 is about 277.3363047224.

Adding to 21331440 its reverse (4413312), we get a palindrome (25744752).

The spelling of 21331440 in words is "twenty-one million, three hundred thirty-one thousand, four hundred forty".