18516121 has 4 divisors (see below), whose sum is σ = 19940452. Its totient is φ = 17091792.

The previous prime is 18516097. The next prime is 18516131. The reversal of 18516121 is 12161581.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12161581 = 73 ⋅166597.

It can be written as a sum of positive squares in 2 ways, for example, as 1177225 + 17338896 = 1085^2 + 4164^2 .

It is a cyclic number.

It is not a de Polignac number, because 18516121 - 2⁷ = 18515993 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18516131) 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, 712146 + ... + 712171.

It is an arithmetic number, because the mean of its divisors is an integer number (4985113).

Almost surely, 2^18516121 is an apocalyptic number.

It is an amenable number.

18516121 is a deficient number, since it is larger than the sum of its proper divisors (1424331).

18516121 is a wasteful number, since it uses less digits than its factorization.

18516121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1424330.

The product of its digits is 480, while the sum is 25.

The square root of 18516121 is about 4303.0362536237. The cubic root of 18516121 is about 264.5554240317. Note that the first 3 decimals are identical.

The spelling of 18516121 in words is "eighteen million, five hundred sixteen thousand, one hundred twenty-one".