218656993 has 2 divisors, whose sum is σ = 218656994. Its totient is φ = 218656992.

The previous prime is 218656969. The next prime is 218657003. The reversal of 218656993 is 399656812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 216325264 + 2331729 = 14708^2 + 1527^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-218656993 is a prime.

It is not a weakly prime, because it can be changed into another prime (218656903) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 109328496 + 109328497.

It is an arithmetic number, because the mean of its divisors is an integer number (109328497).

Almost surely, 2^218656993 is an apocalyptic number.

It is an amenable number.

218656993 is a deficient number, since it is larger than the sum of its proper divisors (1).

218656993 is an equidigital number, since it uses as much as digits as its factorization.

218656993 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 699840, while the sum is 49.

The square root of 218656993 is about 14787.0549129974. The cubic root of 218656993 is about 602.4501596140.

The spelling of 218656993 in words is "two hundred eighteen million, six hundred fifty-six thousand, nine hundred ninety-three".