21453840 has 120 divisors (see below), whose sum is σ = 73120320. Its totient is φ = 5636352.

The previous prime is 21453833. The next prime is 21453853. The reversal of 21453840 is 4835412.

It is a tau number, because it is divible by the number of its divisors (120).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 59581 + ... + 59939.

It is an arithmetic number, because the mean of its divisors is an integer number (609336).

Almost surely, 2^21453840 is an apocalyptic number.

21453840 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 21453840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36560160).

21453840 is an abundant number, since it is smaller than the sum of its proper divisors (51666480).

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

21453840 is a wasteful number, since it uses less digits than its factorization.

21453840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 461 (or 452 counting only the distinct ones).

The product of its (nonzero) digits is 3840, while the sum is 27.

The square root of 21453840 is about 4631.8290123881. The cubic root of 21453840 is about 277.8657461239.

The spelling of 21453840 in words is "twenty-one million, four hundred fifty-three thousand, eight hundred forty".