18945281 has 2 divisors, whose sum is σ = 18945282. Its totient is φ = 18945280.

The previous prime is 18945263. The next prime is 18945287. The reversal of 18945281 is 18254981.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11155600 + 7789681 = 3340^2 + 2791^2 .

It is a cyclic number.

It is not a de Polignac number, because 18945281 - 2⁶ = 18945217 is a prime.

It is a super-2 number, since 2×18945281² = 717847344337922, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (18945287) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9472640 + 9472641.

It is an arithmetic number, because the mean of its divisors is an integer number (9472641).

Almost surely, 2^18945281 is an apocalyptic number.

It is an amenable number.

18945281 is a deficient number, since it is larger than the sum of its proper divisors (1).

18945281 is an equidigital number, since it uses as much as digits as its factorization.

18945281 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 23040, while the sum is 38.

The square root of 18945281 is about 4352.6177181094. The cubic root of 18945281 is about 266.5837566902.

The spelling of 18945281 in words is "eighteen million, nine hundred forty-five thousand, two hundred eighty-one".