218969991 has 12 divisors (see below), whose sum is σ = 319193160. Its totient is φ = 144640080.

The previous prime is 218969987. The next prime is 218970001. The reversal of 218969991 is 199969812.

It is not a de Polignac number, because 218969991 - 2² = 218969987 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (218969921) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 110625 + ... + 112586.

It is an arithmetic number, because the mean of its divisors is an integer number (26599430).

Almost surely, 2^218969991 is an apocalyptic number.

218969991 is a deficient number, since it is larger than the sum of its proper divisors (100223169).

218969991 is a wasteful number, since it uses less digits than its factorization.

218969991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 223326 (or 223323 counting only the distinct ones).

The product of its digits is 629856, while the sum is 54.

The square root of 218969991 is about 14797.6346420636. The cubic root of 218969991 is about 602.7374829836.

The spelling of 218969991 in words is "two hundred eighteen million, nine hundred sixty-nine thousand, nine hundred ninety-one".