18381257 has 2 divisors, whose sum is σ = 18381258. Its totient is φ = 18381256.

The previous prime is 18381239. The next prime is 18381269. The reversal of 18381257 is 75218381.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16128256 + 2253001 = 4016^2 + 1501^2 .

It is a cyclic number.

It is not a de Polignac number, because 18381257 - 2⁸ = 18381001 is a prime.

It is not a weakly prime, because it can be changed into another prime (18381217) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9190628 + 9190629.

It is an arithmetic number, because the mean of its divisors is an integer number (9190629).

Almost surely, 2^18381257 is an apocalyptic number.

It is an amenable number.

18381257 is a deficient number, since it is larger than the sum of its proper divisors (1).

18381257 is an equidigital number, since it uses as much as digits as its factorization.

18381257 is an evil number, because the sum of its binary digits is even.

The product of its digits is 13440, while the sum is 35.

The square root of 18381257 is about 4287.3368190521. The cubic root of 18381257 is about 263.9115530541.

The spelling of 18381257 in words is "eighteen million, three hundred eighty-one thousand, two hundred fifty-seven".