11661 has 12 divisors (see below), whose sum is σ = 17568. Its totient is φ = 6864.

The previous prime is 11657. The next prime is 11677. The reversal of 11661 is 16611.

11661 = T₁₆ + T₁₇ + ... + T₄₁.

It is not a de Polignac number, because 11661 - 2² = 11657 is a prime.

It is a plaindrome in base 7.

It is a nialpdrome in base 11 and base 13.

It is a self number, because there is not a number n which added to its sum of digits gives 11661.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (11621) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 496 + ... + 518.

It is an arithmetic number, because the mean of its divisors is an integer number (1464).

2¹¹⁶⁶¹ is an apocalyptic number.

It is an amenable number.

11661 is a deficient number, since it is larger than the sum of its proper divisors (5907).

11661 is a wasteful number, since it uses less digits than its factorization.

11661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 52 (or 39 counting only the distinct ones).

The product of its digits is 36, while the sum is 15.

The square root of 11661 is about 107.9861102179. The cubic root of 11661 is about 22.6766344088.

Subtracting 11661 from its reverse (16611), we obtain a triangular number (4950 = T₉₉).

The spelling of 11661 in words is "eleven thousand, six hundred sixty-one".