21189870 has 64 divisors (see below), whose sum is σ = 60863040. Its totient is φ = 5215104.

The previous prime is 21189827. The next prime is 21189899. The reversal of 21189870 is 7898112.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 492 + ... + 6528.

It is an arithmetic number, because the mean of its divisors is an integer number (950985).

Almost surely, 2^21189870 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21189870, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30431520).

21189870 is an abundant number, since it is smaller than the sum of its proper divisors (39673170).

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

21189870 is a wasteful number, since it uses less digits than its factorization.

21189870 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6066 (or 6060 counting only the distinct ones).

The product of its (nonzero) digits is 8064, while the sum is 36.

The square root of 21189870 is about 4603.2455941433. The cubic root of 21189870 is about 276.7214114019.

The spelling of 21189870 in words is "twenty-one million, one hundred eighty-nine thousand, eight hundred seventy".