1218391 has 2 divisors, whose sum is σ = 1218392. Its totient is φ = 1218390.

The previous prime is 1218383. The next prime is 1218401. The reversal of 1218391 is 1938121.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 1218391 - 2³ = 1218383 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1218691) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 609195 + 609196.

It is an arithmetic number, because the mean of its divisors is an integer number (609196).

2^1218391 is an apocalyptic number.

1218391 is a deficient number, since it is larger than the sum of its proper divisors (1).

1218391 is an equidigital number, since it uses as much as digits as its factorization.

1218391 is an evil number, because the sum of its binary digits is even.

The product of its digits is 432, while the sum is 25.

The square root of 1218391 is about 1103.8075013335. The cubic root of 1218391 is about 106.8059779136.

The spelling of 1218391 in words is "one million, two hundred eighteen thousand, three hundred ninety-one".