18121657 has 4 divisors (see below), whose sum is σ = 18130176. Its totient is φ = 18113140.

The previous prime is 18121651. The next prime is 18121667. The reversal of 18121657 is 75612181.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 18121657 - 2¹¹ = 18119609 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18121651) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1932 + ... + 6322.

It is an arithmetic number, because the mean of its divisors is an integer number (4532544).

Almost surely, 2^18121657 is an apocalyptic number.

It is an amenable number.

18121657 is a deficient number, since it is larger than the sum of its proper divisors (8519).

18121657 is an equidigital number, since it uses as much as digits as its factorization.

18121657 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8518.

The product of its digits is 3360, while the sum is 31.

The square root of 18121657 is about 4256.9539579375. The cubic root of 18121657 is about 262.6632429818.

The spelling of 18121657 in words is "eighteen million, one hundred twenty-one thousand, six hundred fifty-seven".