20018 has 4 divisors (see below), whose sum is σ = 30030. Its totient is φ = 10008.

The previous prime is 20011. The next prime is 20021. The reversal of 20018 is 81002.

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

It can be written as a sum of positive squares in only one way, i.e., 10609 + 9409 = 103^2 + 97^2 .

20018 is a modest number, since divided by 18 gives 2 as remainder.

It is a Curzon number.

It is a plaindrome in base 7.

It is a junction number, because it is equal to n+sod(n) for n = 19990 and 20008.

It is not an unprimeable number, because it can be changed into a prime (20011) by changing a digit.

20018 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5003 + ... + 5006.

2²⁰⁰¹⁸ is an apocalyptic number.

20018 is a deficient number, since it is larger than the sum of its proper divisors (10012).

20018 is a wasteful number, since it uses less digits than its factorization.

20018 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10011.

The product of its (nonzero) digits is 16, while the sum is 11.

The square root of 20018 is about 141.4849815351. The cubic root of 20018 is about 27.1523169770.

Subtracting from 20018 its product of nonzero digits (16), we obtain a palindrome (20002).

It can be divided in two parts, 200 and 18, that multiplied together give a square (3600 = 60²).

The spelling of 20018 in words is "twenty thousand, eighteen".