2001220181 has 2 divisors, whose sum is σ = 2001220182. Its totient is φ = 2001220180.

The previous prime is 2001220171. The next prime is 2001220211. The reversal of 2001220181 is 1810221002.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1325688100 + 675532081 = 36410^2 + 25991^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-2001220181 is a prime.

It is a super-3 number, since 3×2001220181³ (a number of 29 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2001220141) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1000610090 + 1000610091.

It is an arithmetic number, because the mean of its divisors is an integer number (1000610091).

Almost surely, 2^2001220181 is an apocalyptic number.

It is an amenable number.

2001220181 is a deficient number, since it is larger than the sum of its proper divisors (1).

2001220181 is an equidigital number, since it uses as much as digits as its factorization.

2001220181 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 64, while the sum is 17.

The square root of 2001220181 is about 44734.9995082150. Note that the first 3 decimals coincide. The cubic root of 2001220181 is about 1260.1772197608.

Adding to 2001220181 its reverse (1810221002), we get a palindrome (3811441183).

The spelling of 2001220181 in words is "two billion, one million, two hundred twenty thousand, one hundred eighty-one".