129661 has 4 divisors (see below), whose sum is σ = 148192. Its totient is φ = 111132.

The previous prime is 129643. The next prime is 129671. The reversal of 129661 is 166921.

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: 166921 = 71 ⋅2351.

It is not a de Polignac number, because 129661 - 2⁵ = 129629 is a prime.

It is a Duffinian number.

129661 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (129631) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9255 + ... + 9268.

It is an arithmetic number, because the mean of its divisors is an integer number (37048).

2¹²⁹⁶⁶¹ is an apocalyptic number.

It is an amenable number.

129661 is a deficient number, since it is larger than the sum of its proper divisors (18531).

129661 is an equidigital number, since it uses as much as digits as its factorization.

129661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18530.

The product of its digits is 648, while the sum is 25.

The square root of 129661 is about 360.0847122553. The cubic root of 129661 is about 50.6138983938.

The spelling of 129661 in words is "one hundred twenty-nine thousand, six hundred sixty-one".