191661 has 8 divisors (see below), whose sum is σ = 264480. Its totient is φ = 123312.

The previous prime is 191657. The next prime is 191669. The reversal of 191661 is 166191.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 191661 - 2² = 191657 is a prime.

191661 is a lucky number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 191661.

It is not an unprimeable number, because it can be changed into a prime (191669) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1015 + ... + 1188.

It is an arithmetic number, because the mean of its divisors is an integer number (33060).

2¹⁹¹⁶⁶¹ is an apocalyptic number.

It is an amenable number.

191661 is a deficient number, since it is larger than the sum of its proper divisors (72819).

191661 is a wasteful number, since it uses less digits than its factorization.

191661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2235.

The product of its digits is 324, while the sum is 24.

The square root of 191661 is about 437.7910460482. The cubic root of 191661 is about 57.6560098513.

The spelling of 191661 in words is "one hundred ninety-one thousand, six hundred sixty-one".