20018021 has 2 divisors, whose sum is σ = 20018022. Its totient is φ = 20018020.

The previous prime is 20018017. The next prime is 20018069. The reversal of 20018021 is 12081002.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19936225 + 81796 = 4465^2 + 286^2 .

It is a cyclic number.

It is not a de Polignac number, because 20018021 - 2² = 20018017 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 20017987 and 20018005.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20018071) 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, 10009010 + 10009011.

It is an arithmetic number, because the mean of its divisors is an integer number (10009011).

Almost surely, 2^20018021 is an apocalyptic number.

It is an amenable number.

20018021 is a deficient number, since it is larger than the sum of its proper divisors (1).

20018021 is an equidigital number, since it uses as much as digits as its factorization.

20018021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 32, while the sum is 14.

The square root of 20018021 is about 4474.1503103941. The cubic root of 20018021 is about 271.5232647181.

Adding to 20018021 its reverse (12081002), we get a palindrome (32099023).

The spelling of 20018021 in words is "twenty million, eighteen thousand, twenty-one".