21866218 has 8 divisors (see below), whose sum is σ = 35781120. Its totient is φ = 9939180.

The previous prime is 21866213. The next prime is 21866219. The reversal of 21866218 is 81266812.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not an unprimeable number, because it can be changed into a prime (21866213) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 496938 + ... + 496981.

It is an arithmetic number, because the mean of its divisors is an integer number (4472640).

Almost surely, 2^21866218 is an apocalyptic number.

21866218 is a deficient number, since it is larger than the sum of its proper divisors (13914902).

21866218 is a wasteful number, since it uses less digits than its factorization.

21866218 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 993932.

The product of its digits is 9216, while the sum is 34.

The square root of 21866218 is about 4676.1328039310. The cubic root of 21866218 is about 279.6348045059.

The spelling of 21866218 in words is "twenty-one million, eight hundred sixty-six thousand, two hundred eighteen".