18345781 has 2 divisors, whose sum is σ = 18345782. Its totient is φ = 18345780.

The previous prime is 18345731. The next prime is 18345787. The reversal of 18345781 is 18754381.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13439556 + 4906225 = 3666^2 + 2215^2 .

It is a cyclic number.

It is not a de Polignac number, because 18345781 - 2⁷ = 18345653 is a prime.

It is a super-2 number, since 2×18345781² = 673135360999922, which contains 22 as substring.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 18345781.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18345787) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9172890 + 9172891.

It is an arithmetic number, because the mean of its divisors is an integer number (9172891).

Almost surely, 2^18345781 is an apocalyptic number.

It is an amenable number.

18345781 is a deficient number, since it is larger than the sum of its proper divisors (1).

18345781 is an equidigital number, since it uses as much as digits as its factorization.

18345781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 26880, while the sum is 37.

The square root of 18345781 is about 4283.1975205447. The cubic root of 18345781 is about 263.7416597769.

The spelling of 18345781 in words is "eighteen million, three hundred forty-five thousand, seven hundred eighty-one".