18673981 has 2 divisors, whose sum is σ = 18673982. Its totient is φ = 18673980.

The previous prime is 18673933. The next prime is 18674009. The reversal of 18673981 is 18937681.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18619225 + 54756 = 4315^2 + 234^2 .

It is a cyclic number.

It is not a de Polignac number, because 18673981 - 2⁹ = 18673469 is a prime.

It is a super-2 number, since 2×18673981² = 697435132776722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18671981) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9336990 + 9336991.

It is an arithmetic number, because the mean of its divisors is an integer number (9336991).

Almost surely, 2^18673981 is an apocalyptic number.

It is an amenable number.

18673981 is a deficient number, since it is larger than the sum of its proper divisors (1).

18673981 is an equidigital number, since it uses as much as digits as its factorization.

18673981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 72576, while the sum is 43.

The square root of 18673981 is about 4321.3401856369. The cubic root of 18673981 is about 265.3051238005.

The spelling of 18673981 in words is "eighteen million, six hundred seventy-three thousand, nine hundred eighty-one".