129666121 has 4 divisors (see below), whose sum is σ = 139640452. Its totient is φ = 119691792.

The previous prime is 129666109. The next prime is 129666139. The reversal of 129666121 is 121666921.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 121666921 = 173 ⋅703277.

It can be written as a sum of positive squares in 2 ways, for example, as 25401600 + 104264521 = 5040^2 + 10211^2 .

It is a cyclic number.

It is not a de Polignac number, because 129666121 - 2¹⁵ = 129633353 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (129666151) 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, 4987146 + ... + 4987171.

It is an arithmetic number, because the mean of its divisors is an integer number (34910113).

Almost surely, 2^129666121 is an apocalyptic number.

It is an amenable number.

129666121 is a deficient number, since it is larger than the sum of its proper divisors (9974331).

129666121 is an equidigital number, since it uses as much as digits as its factorization.

129666121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9974330.

The product of its digits is 7776, while the sum is 34.

The square root of 129666121 is about 11387.1032751969. The cubic root of 129666121 is about 506.1456472207.

The spelling of 129666121 in words is "one hundred twenty-nine million, six hundred sixty-six thousand, one hundred twenty-one".