18910181 has 2 divisors, whose sum is σ = 18910182. Its totient is φ = 18910180.

The previous prime is 18910169. The next prime is 18910207. The reversal of 18910181 is 18101981.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17297281 + 1612900 = 4159^2 + 1270^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18910181 is a prime.

It is a super-2 number, since 2×18910181² = 715189890905522, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18910481) 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, 9455090 + 9455091.

It is an arithmetic number, because the mean of its divisors is an integer number (9455091).

Almost surely, 2^18910181 is an apocalyptic number.

It is an amenable number.

18910181 is a deficient number, since it is larger than the sum of its proper divisors (1).

18910181 is an equidigital number, since it uses as much as digits as its factorization.

18910181 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 576, while the sum is 29.

The square root of 18910181 is about 4348.5837924547. The cubic root of 18910181 is about 266.4190213056.

It can be divided in two parts, 18910 and 181, that added together give a palindrome (19091).

The spelling of 18910181 in words is "eighteen million, nine hundred ten thousand, one hundred eighty-one".