1218668191 has 4 divisors (see below), whose sum is σ = 1312411912. Its totient is φ = 1124924472.

The previous prime is 1218668177. The next prime is 1218668207. The reversal of 1218668191 is 1918668121.

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 1218668191 - 2¹¹ = 1218666143 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1218668491) 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, 46871841 + ... + 46871866.

It is an arithmetic number, because the mean of its divisors is an integer number (328102978).

Almost surely, 2^1218668191 is an apocalyptic number.

1218668191 is a deficient number, since it is larger than the sum of its proper divisors (93743721).

1218668191 is an equidigital number, since it uses as much as digits as its factorization.

1218668191 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 93743720.

The product of its digits is 41472, while the sum is 43.

The square root of 1218668191 is about 34909.4283969245. The cubic root of 1218668191 is about 1068.1407695865.

The spelling of 1218668191 in words is "one billion, two hundred eighteen million, six hundred sixty-eight thousand, one hundred ninety-one".