21437440 has 88 divisors (see below), whose sum is σ = 53058240. Its totient is φ = 8306688.

The previous prime is 21437431. The next prime is 21437441. The reversal of 21437440 is 4473412.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21437441) 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, 271321 + ... + 271399.

Almost surely, 2^21437440 is an apocalyptic number.

21437440 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 21437440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26529120).

21437440 is an abundant number, since it is smaller than the sum of its proper divisors (31620800).

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

21437440 is an equidigital number, since it uses as much as digits as its factorization.

21437440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 157 (or 139 counting only the distinct ones).

The product of its (nonzero) digits is 2688, while the sum is 25.

The square root of 21437440 is about 4630.0583149675. The cubic root of 21437440 is about 277.7949249267.

The spelling of 21437440 in words is "twenty-one million, four hundred thirty-seven thousand, four hundred forty".