218866891 has 4 divisors (see below), whose sum is σ = 231741432. Its totient is φ = 205992352.

The previous prime is 218866883. The next prime is 218866927. The reversal of 218866891 is 198668812.

218866891 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 218866891 - 2³ = 218866883 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (218866591) 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, 6437245 + ... + 6437278.

It is an arithmetic number, because the mean of its divisors is an integer number (57935358).

Almost surely, 2^218866891 is an apocalyptic number.

218866891 is a deficient number, since it is larger than the sum of its proper divisors (12874541).

218866891 is a wasteful number, since it uses less digits than its factorization.

218866891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12874540.

The product of its digits is 331776, while the sum is 49.

The square root of 218866891 is about 14794.1505670316. The cubic root of 218866891 is about 602.6428703386.

The spelling of 218866891 in words is "two hundred eighteen million, eight hundred sixty-six thousand, eight hundred ninety-one".