7218391 has 2 divisors, whose sum is σ = 7218392. Its totient is φ = 7218390.

The previous prime is 7218371. The next prime is 7218397. The reversal of 7218391 is 1938127.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 7218391 - 2¹¹ = 7216343 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (7218397) 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 as a sum of consecutive naturals, namely, 3609195 + 3609196.

It is an arithmetic number, because the mean of its divisors is an integer number (3609196).

Almost surely, 2^7218391 is an apocalyptic number.

7218391 is a deficient number, since it is larger than the sum of its proper divisors (1).

7218391 is an equidigital number, since it uses as much as digits as its factorization.

7218391 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3024, while the sum is 31.

The square root of 7218391 is about 2686.7063479286. The cubic root of 7218391 is about 193.2621474613.

The spelling of 7218391 in words is "seven million, two hundred eighteen thousand, three hundred ninety-one".