21866187 has 16 divisors (see below), whose sum is σ = 33819392. Its totient is φ = 12307680.

The previous prime is 21866137. The next prime is 21866189. The reversal of 21866187 is 78166812.

It is not a de Polignac number, because 21866187 - 2¹⁴ = 21849803 is a prime.

It is a Smith number, since the sum of its digits (39) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21866189) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6364 + ... + 9177.

It is an arithmetic number, because the mean of its divisors is an integer number (2113712).

Almost surely, 2^21866187 is an apocalyptic number.

21866187 is a deficient number, since it is larger than the sum of its proper divisors (11953205).

21866187 is a wasteful number, since it uses less digits than its factorization.

21866187 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15618.

The product of its digits is 32256, while the sum is 39.

The square root of 21866187 is about 4676.1294892250. The cubic root of 21866187 is about 279.6346723587.

The spelling of 21866187 in words is "twenty-one million, eight hundred sixty-six thousand, one hundred eighty-seven".