2661 has 4 divisors (see below), whose sum is σ = 3552.
Its totient is φ = 1772.
The previous prime is 2659. The next prime is 2663. The reversal of 2661 is 1662.
Subtracting from 2661 its reverse (1662), we obtain a palindrome (999).
2661 = 132 + 142 + ... + 212.
2661 is nontrivially palindromic in base 2.
2661 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.
It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.
It is an interprime number because it is at equal distance from previous prime (2659) and next prime (2663).
It is a cyclic number.
It is not a de Polignac number, because 2661 - 21 = 2659 is a prime.
It is a D-number.
It is a Curzon number.
2661 is a lucky number.
It is a plaindrome in base 11 and base 13.
It is a nialpdrome in base 14 and base 16.
It is a self number, because there is not a number n which added to its sum of digits gives 2661.
It is a congruent number.
It is not an unprimeable number, because it can be changed into a prime (2663) by changing a digit.
It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 441 + ... + 446.
It is an arithmetic number, because the mean of its divisors is an integer number (888).
It is an amenable number.
2661 is a deficient number, since it is larger than the sum of its proper divisors (891).
2661 is an equidigital number, since it uses as much as digits as its factorization.
2661 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 890.
The product of its digits is 72, while the sum is 15.
The square root of 2661 is about 51.5848815061.
The cubic root of 2661 is about 13.8573959030.
The spelling of 2661 in words is "two thousand, six hundred sixty-one".