18642181 has 2 divisors, whose sum is σ = 18642182. Its totient is φ = 18642180.

The previous prime is 18642179. The next prime is 18642187. The reversal of 18642181 is 18124681.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17986081 + 656100 = 4241^2 + 810^2 .

It is a cyclic number.

It is not a de Polignac number, because 18642181 - 2¹ = 18642179 is a prime.

It is a super-2 number, since 2×18642181² = 695061824873522, which contains 22 as substring.

Together with 18642179, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18642187) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9321090 + 9321091.

It is an arithmetic number, because the mean of its divisors is an integer number (9321091).

Almost surely, 2^18642181 is an apocalyptic number.

It is an amenable number.

18642181 is a deficient number, since it is larger than the sum of its proper divisors (1).

18642181 is an equidigital number, since it uses as much as digits as its factorization.

18642181 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3072, while the sum is 31.

The square root of 18642181 is about 4317.6592037816. The cubic root of 18642181 is about 265.1544418358.

The spelling of 18642181 in words is "eighteen million, six hundred forty-two thousand, one hundred eighty-one".