18221257 has 2 divisors, whose sum is σ = 18221258. Its totient is φ = 18221256.

The previous prime is 18221243. The next prime is 18221339. The reversal of 18221257 is 75212281.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17131321 + 1089936 = 4139^2 + 1044^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18221257 is a prime.

It is equal to p_1164493 and since 18221257 and 1164493 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (18222257) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9110628 + 9110629.

It is an arithmetic number, because the mean of its divisors is an integer number (9110629).

Almost surely, 2^18221257 is an apocalyptic number.

It is an amenable number.

18221257 is a deficient number, since it is larger than the sum of its proper divisors (1).

18221257 is an equidigital number, since it uses as much as digits as its factorization.

18221257 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2240, while the sum is 28.

The square root of 18221257 is about 4268.6364333356. The cubic root of 18221257 is about 263.1435794058.

The spelling of 18221257 in words is "eighteen million, two hundred twenty-one thousand, two hundred fifty-seven".