18391213 has 2 divisors, whose sum is σ = 18391214. Its totient is φ = 18391212.

The previous prime is 18391207. The next prime is 18391271. The reversal of 18391213 is 31219381.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11009124 + 7382089 = 3318^2 + 2717^2 .

It is a cyclic number.

It is not a de Polignac number, because 18391213 - 2⁵ = 18391181 is a prime.

It is a super-2 number, since 2×18391213² = 676473431222738, which contains 22 as substring.

It is equal to p_1174690 and since 18391213 and 1174690 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18391013) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9195606 + 9195607.

It is an arithmetic number, because the mean of its divisors is an integer number (9195607).

Almost surely, 2^18391213 is an apocalyptic number.

It is an amenable number.

18391213 is a deficient number, since it is larger than the sum of its proper divisors (1).

18391213 is an equidigital number, since it uses as much as digits as its factorization.

18391213 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1296, while the sum is 28.

The square root of 18391213 is about 4288.4977556249. The cubic root of 18391213 is about 263.9591926902.

The spelling of 18391213 in words is "eighteen million, three hundred ninety-one thousand, two hundred thirteen".