18943381 has 2 divisors, whose sum is σ = 18943382. Its totient is φ = 18943380.

The previous prime is 18943363. The next prime is 18943417. The reversal of 18943381 is 18334981.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18748900 + 194481 = 4330^2 + 441^2 .

It is a cyclic number.

It is not a de Polignac number, because 18943381 - 2¹¹ = 18941333 is a prime.

It is a super-2 number, since 2×18943381² = 717703367422322, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 18943381.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18943081) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9471690 + 9471691.

It is an arithmetic number, because the mean of its divisors is an integer number (9471691).

Almost surely, 2^18943381 is an apocalyptic number.

It is an amenable number.

18943381 is a deficient number, since it is larger than the sum of its proper divisors (1).

18943381 is an equidigital number, since it uses as much as digits as its factorization.

18943381 is an evil number, because the sum of its binary digits is even.

The product of its digits is 20736, while the sum is 37.

The square root of 18943381 is about 4352.3994531752. The cubic root of 18943381 is about 266.5748446016.

Subtracting from 18943381 its reverse (18334981), we obtain a square (608400 = 780²).

The spelling of 18943381 in words is "eighteen million, nine hundred forty-three thousand, three hundred eighty-one".