18021518 has 4 divisors (see below), whose sum is σ = 27032280. Its totient is φ = 9010758.

The previous prime is 18021511. The next prime is 18021527. The reversal of 18021518 is 81512081.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 81512081 = 7 ⋅11644583.

It is a super-2 number, since 2×18021518² = 649550222048648, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18021511) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4505378 + ... + 4505381.

It is an arithmetic number, because the mean of its divisors is an integer number (6758070).

Almost surely, 2^18021518 is an apocalyptic number.

18021518 is a deficient number, since it is larger than the sum of its proper divisors (9010762).

18021518 is an equidigital number, since it uses as much as digits as its factorization.

18021518 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9010761.

The product of its (nonzero) digits is 640, while the sum is 26.

The square root of 18021518 is about 4245.1758503035. The cubic root of 18021518 is about 262.1785295257.

Adding to 18021518 its reverse (81512081), we get a palindrome (99533599).

The spelling of 18021518 in words is "eighteen million, twenty-one thousand, five hundred eighteen".