2161 has 2 divisors, whose sum is σ = 2162.
Its totient is φ = 2160.
The previous prime is 2153. The next prime is 2179. The reversal of 2161 is 1612.
Adding to 2161 its reverse (1612), we get a palindrome (3773).
2161 is an esthetic number in base 5, because in such base its adjacent digits differ by 1.
It is a weak prime.
It can be written as a sum of positive squares in only one way, i.e., 1936 + 225 = 44^2 + 15^2
It is a cyclic number.
It is not a de Polignac number, because 2161 - 23 = 2153 is a prime.
It is an alternating number because its digits alternate between even and odd.
It is a nialpdrome in base 13, base 15 and base 16.
It is not a weakly prime, because it can be changed into another prime (2111) by changing a digit.
It is a pernicious number, because its binary representation contains a prime number (5) of ones.
It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1080 + 1081.
It is an arithmetic number, because the mean of its divisors is an integer number (1081).
22161 is an apocalyptic number.
It is an amenable number.
2161 is a deficient number, since it is larger than the sum of its proper divisors (1).
2161 is an equidigital number, since it uses as much as digits as its factorization.
2161 is an odious number, because the sum of its binary digits is odd.
The product of its digits is 12, while the sum is 10.
The square root of 2161 is about 46.4865571967.
The cubic root of 2161 is about 12.9286026794.
The spelling of 2161 in words is "two thousand, one hundred sixty-one".