18778381 has 2 divisors, whose sum is σ = 18778382. Its totient is φ = 18778380.

The previous prime is 18778363. The next prime is 18778433. The reversal of 18778381 is 18387781.

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., 17892900 + 885481 = 4230^2 + 941^2 .

It is a cyclic number.

It is not a de Polignac number, because 18778381 - 2¹¹ = 18776333 is a prime.

It is a super-2 number, since 2×18778381² = 705255185962322, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18778181) 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, 9389190 + 9389191.

It is an arithmetic number, because the mean of its divisors is an integer number (9389191).

Almost surely, 2^18778381 is an apocalyptic number.

It is an amenable number.

18778381 is a deficient number, since it is larger than the sum of its proper divisors (1).

18778381 is an equidigital number, since it uses as much as digits as its factorization.

18778381 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 75264, while the sum is 43.

The square root of 18778381 is about 4333.4029353385. The cubic root of 18778381 is about 265.7986161122.

The spelling of 18778381 in words is "eighteen million, seven hundred seventy-eight thousand, three hundred eighty-one".