18218261 has 2 divisors, whose sum is σ = 18218262. Its totient is φ = 18218260.

The previous prime is 18218257. The next prime is 18218267. The reversal of 18218261 is 16281281.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12117361 + 6100900 = 3481^2 + 2470^2 .

It is a cyclic number.

It is not a de Polignac number, because 18218261 - 2² = 18218257 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18218267) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9109130 + 9109131.

It is an arithmetic number, because the mean of its divisors is an integer number (9109131).

Almost surely, 2^18218261 is an apocalyptic number.

It is an amenable number.

18218261 is a deficient number, since it is larger than the sum of its proper divisors (1).

18218261 is an equidigital number, since it uses as much as digits as its factorization.

18218261 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1536, while the sum is 29.

The square root of 18218261 is about 4268.2854871716. The cubic root of 18218261 is about 263.1291562996.

The spelling of 18218261 in words is "eighteen million, two hundred eighteen thousand, two hundred sixty-one".