20161 has 2 divisors, whose sum is σ = 20162. Its totient is φ = 20160.

The previous prime is 20149. The next prime is 20173. The reversal of 20161 is 16102.

It is a balanced prime because it is at equal distance from previous prime (20149) and next prime (20173).

It can be written as a sum of positive squares in only one way, i.e., 18225 + 1936 = 135^2 + 44^2 .

It is a cyclic number.

It is not a de Polignac number, because 20161 - 2⁵ = 20129 is a prime.

It is not a weakly prime, because it can be changed into another prime (20101) by changing a digit.

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, 10080 + 10081.

It is an arithmetic number, because the mean of its divisors is an integer number (10081).

2²⁰¹⁶¹ is an apocalyptic number.

20161 is the 64-th centered decagonal number.

It is an amenable number.

20161 is a deficient number, since it is larger than the sum of its proper divisors (1).

20161 is an equidigital number, since it uses as much as digits as its factorization.

20161 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 12, while the sum is 10.

The square root of 20161 is about 141.9894362268. The cubic root of 20161 is about 27.2168184625.

Adding to 20161 its reverse (16102), we get a palindrome (36263).

It can be divided in two parts, 201 and 61, that added together give a palindrome (262).

The spelling of 20161 in words is "twenty thousand, one hundred sixty-one".