218668993 has 4 divisors (see below), whose sum is σ = 218699568. Its totient is φ = 218638420.

The previous prime is 218668991. The next prime is 218668997. The reversal of 218668993 is 399866812.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 218668993 - 2¹ = 218668991 is a prime.

It is a super-2 number, since 2×218668993² = 95632256999268098, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 218668993.

It is not an unprimeable number, because it can be changed into a prime (218668991) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1830 + ... + 20992.

It is an arithmetic number, because the mean of its divisors is an integer number (54674892).

Almost surely, 2^218668993 is an apocalyptic number.

It is an amenable number.

218668993 is a deficient number, since it is larger than the sum of its proper divisors (30575).

218668993 is a wasteful number, since it uses less digits than its factorization.

218668993 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 30574.

The product of its digits is 1119744, while the sum is 52.

The square root of 218668993 is about 14787.4606677414. The cubic root of 218668993 is about 602.4611803297.

The spelling of 218668993 in words is "two hundred eighteen million, six hundred sixty-eight thousand, nine hundred ninety-three".