21321440 has 48 divisors (see below), whose sum is σ = 57570912. Its totient is φ = 7309824.

The previous prime is 21321431. The next prime is 21321449. The reversal of 21321440 is 4412312.

It is an interprime number because it is at equal distance from previous prime (21321431) and next prime (21321449).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21321449) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8399 + ... + 10638.

It is an arithmetic number, because the mean of its divisors is an integer number (1199394).

Almost surely, 2^21321440 is an apocalyptic number.

21321440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21321440 is an abundant number, since it is smaller than the sum of its proper divisors (36249472).

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

21321440 is a wasteful number, since it uses less digits than its factorization.

21321440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19059 (or 19051 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 17.

The square root of 21321440 is about 4617.5144829226. The cubic root of 21321440 is about 277.2929603047.

Adding to 21321440 its reverse (4412312), we get a palindrome (25733752).

The spelling of 21321440 in words is "twenty-one million, three hundred twenty-one thousand, four hundred forty".