18157121 has 4 divisors (see below), whose sum is σ = 18647892. Its totient is φ = 17666352.

The previous prime is 18157109. The next prime is 18157133. The reversal of 18157121 is 12175181.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (18157109) and next prime (18157133).

It can be written as a sum of positive squares in 2 ways, for example, as 12816400 + 5340721 = 3580^2 + 2311^2 .

It is a cyclic number.

It is not a de Polignac number, because 18157121 - 2⁶ = 18157057 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18157171) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 245330 + ... + 245403.

It is an arithmetic number, because the mean of its divisors is an integer number (4661973).

Almost surely, 2^18157121 is an apocalyptic number.

It is an amenable number.

18157121 is a deficient number, since it is larger than the sum of its proper divisors (490771).

18157121 is an equidigital number, since it uses as much as digits as its factorization.

18157121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 490770.

The product of its digits is 560, while the sum is 26.

The square root of 18157121 is about 4261.1173417309. The cubic root of 18157121 is about 262.8344749193.

The spelling of 18157121 in words is "eighteen million, one hundred fifty-seven thousand, one hundred twenty-one".