18781313 has 2 divisors, whose sum is σ = 18781314. Its totient is φ = 18781312.

The previous prime is 18781307. The next prime is 18781333. The reversal of 18781313 is 31318781.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18731584 + 49729 = 4328^2 + 223^2 .

It is a cyclic number.

It is not a de Polignac number, because 18781313 - 2⁴ = 18781297 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 18781313.

It is not a weakly prime, because it can be changed into another prime (18781333) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9390656 + 9390657.

It is an arithmetic number, because the mean of its divisors is an integer number (9390657).

Almost surely, 2^18781313 is an apocalyptic number.

It is an amenable number.

18781313 is a deficient number, since it is larger than the sum of its proper divisors (1).

18781313 is an equidigital number, since it uses as much as digits as its factorization.

18781313 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4032, while the sum is 32.

The square root of 18781313 is about 4333.7412243926. The cubic root of 18781313 is about 265.8124490581.

The spelling of 18781313 in words is "eighteen million, seven hundred eighty-one thousand, three hundred thirteen".