18218639 has 2 divisors, whose sum is σ = 18218640. Its totient is φ = 18218638.

The previous prime is 18218617. The next prime is 18218653. The reversal of 18218639 is 93681281.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 18218639 - 2¹⁶ = 18153103 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18218659) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9109319 + 9109320.

It is an arithmetic number, because the mean of its divisors is an integer number (9109320).

Almost surely, 2^18218639 is an apocalyptic number.

18218639 is a deficient number, since it is larger than the sum of its proper divisors (1).

18218639 is an equidigital number, since it uses as much as digits as its factorization.

18218639 is an evil number, because the sum of its binary digits is even.

The product of its digits is 20736, while the sum is 38.

The square root of 18218639 is about 4268.3297670166. The cubic root of 18218639 is about 263.1309761245.

The spelling of 18218639 in words is "eighteen million, two hundred eighteen thousand, six hundred thirty-nine".