159661 has 4 divisors (see below), whose sum is σ = 162112. Its totient is φ = 157212.

The previous prime is 159631. The next prime is 159667. The reversal of 159661 is 166951.

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, and also an emirpimes, since its reverse is a distinct semiprime: 166951 = 73 ⋅2287.

It is a cyclic number.

It is not a de Polignac number, because 159661 - 2⁵ = 159629 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (159667) 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, 1125 + ... + 1258.

It is an arithmetic number, because the mean of its divisors is an integer number (40528).

2¹⁵⁹⁶⁶¹ is an apocalyptic number.

It is an amenable number.

159661 is a deficient number, since it is larger than the sum of its proper divisors (2451).

159661 is an equidigital number, since it uses as much as digits as its factorization.

159661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2450.

The product of its digits is 1620, while the sum is 28.

The square root of 159661 is about 399.5760253068. The cubic root of 159661 is about 54.2499840727.

It can be divided in two parts, 159 and 661, that added together give a triangular number (820 = T₄₀).

The spelling of 159661 in words is "one hundred fifty-nine thousand, six hundred sixty-one".