18731281 has 2 divisors, whose sum is σ = 18731282. Its totient is φ = 18731280.

The previous prime is 18731267. The next prime is 18731299. The reversal of 18731281 is 18213781.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15523600 + 3207681 = 3940^2 + 1791^2 .

It is an emirp because it is prime and its reverse (18213781) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18731281 - 2¹¹ = 18729233 is a prime.

It is a super-2 number, since 2×18731281² = 701721775801922, which contains 22 as substring.

It is a zygodrome in base 16.

It is not a weakly prime, because it can be changed into another prime (18731201) 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, 9365640 + 9365641.

It is an arithmetic number, because the mean of its divisors is an integer number (9365641).

Almost surely, 2^18731281 is an apocalyptic number.

It is an amenable number.

18731281 is a deficient number, since it is larger than the sum of its proper divisors (1).

18731281 is an equidigital number, since it uses as much as digits as its factorization.

18731281 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2688, while the sum is 31.

The square root of 18731281 is about 4327.9649952374. The cubic root of 18731281 is about 265.5762043885.

The spelling of 18731281 in words is "eighteen million, seven hundred thirty-one thousand, two hundred eighty-one".