129999991 has 4 divisors (see below), whose sum is σ = 141818184. Its totient is φ = 118181800.

The previous prime is 129999983. The next prime is 129999997. The reversal of 129999991 is 199999921.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 129999991 - 2³ = 129999983 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 (129999997) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5909080 + ... + 5909101.

It is an arithmetic number, because the mean of its divisors is an integer number (35454546).

Almost surely, 2^129999991 is an apocalyptic number.

129999991 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

129999991 is a deficient number, since it is larger than the sum of its proper divisors (11818193).

129999991 is a wasteful number, since it uses less digits than its factorization.

129999991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11818192.

The product of its digits is 1062882, while the sum is 58.

The square root of 129999991 is about 11401.7538563153. The cubic root of 129999991 is about 506.5796902198.

It can be divided in two parts, 1 and 29999991, that added together give a palindrome (29999992).

The spelling of 129999991 in words is "one hundred twenty-nine million, nine hundred ninety-nine thousand, nine hundred ninety-one".