21365440 has 56 divisors (see below), whose sum is σ = 51297840. Its totient is φ = 8475648.

The previous prime is 21365423. The next prime is 21365441. The reversal of 21365440 is 4456312.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21365441) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 57094 + ... + 57466.

Almost surely, 2^21365440 is an apocalyptic number.

21365440 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 21365440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25648920).

21365440 is an abundant number, since it is smaller than the sum of its proper divisors (29932400).

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

21365440 is a wasteful number, since it uses less digits than its factorization.

21365440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 569 (or 559 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 25.

The square root of 21365440 is about 4622.2764954079. The cubic root of 21365440 is about 277.4835744951.

The spelling of 21365440 in words is "twenty-one million, three hundred sixty-five thousand, four hundred forty".