218730991 has 2 divisors, whose sum is σ = 218730992. Its totient is φ = 218730990.

The previous prime is 218730977. The next prime is 218731001. The reversal of 218730991 is 199037812.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 218730991 - 2¹¹ = 218728943 is a prime.

It is a congruent number.

It is a weakly prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 109365495 + 109365496.

It is an arithmetic number, because the mean of its divisors is an integer number (109365496).

Almost surely, 2^218730991 is an apocalyptic number.

218730991 is a deficient number, since it is larger than the sum of its proper divisors (1).

218730991 is an equidigital number, since it uses as much as digits as its factorization.

218730991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 27216, while the sum is 40.

The square root of 218730991 is about 14789.5568222986. The cubic root of 218730991 is about 602.5181124356.

The spelling of 218730991 in words is "two hundred eighteen million, seven hundred thirty thousand, nine hundred ninety-one".