21408750 has 120 divisors (see below), whose sum is σ = 63598392. Its totient is φ = 5160000.

The previous prime is 21408733. The next prime is 21408781. The reversal of 21408750 is 5780412.

It is a plaindrome in base 16.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 59 ways as a sum of consecutive naturals, for example, 123664 + ... + 123836.

Almost surely, 2^21408750 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21408750, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31799196).

21408750 is an abundant number, since it is smaller than the sum of its proper divisors (42189642).

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

21408750 is a wasteful number, since it uses less digits than its factorization.

21408750 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 212 (or 194 counting only the distinct ones).

The product of its (nonzero) digits is 2240, while the sum is 27.

The square root of 21408750 is about 4626.9590445562. The cubic root of 21408750 is about 277.6709441021.

The spelling of 21408750 in words is "twenty-one million, four hundred eight thousand, seven hundred fifty".