18881281 has 2 divisors, whose sum is σ = 18881282. Its totient is φ = 18881280.

The previous prime is 18881273. The next prime is 18881287. The reversal of 18881281 is 18218881.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13024881 + 5856400 = 3609^2 + 2420^2 .

It is an emirp because it is prime and its reverse (18218881) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18881281 - 2³ = 18881273 is a prime.

It is a super-3 number, since 3×18881281³ (a number of 23 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a self number, because there is not a number n which added to its sum of digits gives 18881281.

It is not a weakly prime, because it can be changed into another prime (18881287) 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, 9440640 + 9440641.

It is an arithmetic number, because the mean of its divisors is an integer number (9440641).

Almost surely, 2^18881281 is an apocalyptic number.

It is an amenable number.

18881281 is a deficient number, since it is larger than the sum of its proper divisors (1).

18881281 is an equidigital number, since it uses as much as digits as its factorization.

18881281 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 8192, while the sum is 37.

The square root of 18881281 is about 4345.2596009905. The cubic root of 18881281 is about 266.2832313948.

The spelling of 18881281 in words is "eighteen million, eight hundred eighty-one thousand, two hundred eighty-one".