21408870 has 64 divisors (see below), whose sum is σ = 59383296. Its totient is φ = 4838400.

The previous prime is 21408851. The next prime is 21408901. The reversal of 21408870 is 7880412.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 19845 + ... + 20895.

It is an arithmetic number, because the mean of its divisors is an integer number (927864).

Almost surely, 2^21408870 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21408870, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29691648).

21408870 is an abundant number, since it is smaller than the sum of its proper divisors (37974426).

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

21408870 is a wasteful number, since it uses less digits than its factorization.

21408870 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1165.

The product of its (nonzero) digits is 3584, while the sum is 30.

The square root of 21408870 is about 4626.9720120182. The cubic root of 21408870 is about 277.6714629001.

The spelling of 21408870 in words is "twenty-one million, four hundred eight thousand, eight hundred seventy".