129999891 has 12 divisors (see below), whose sum is σ = 201632712. Its totient is φ = 74285568.

The previous prime is 129999871. The next prime is 129999911. The reversal of 129999891 is 198999921.

It is an interprime number because it is at equal distance from previous prime (129999871) and next prime (129999911).

It is not a de Polignac number, because 129999891 - 2⁷ = 129999763 is a prime.

It is not an unprimeable number, because it can be changed into a prime (129999871) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 442030 + ... + 442323.

It is an arithmetic number, because the mean of its divisors is an integer number (16802726).

Almost surely, 2^129999891 is an apocalyptic number.

129999891 is a deficient number, since it is larger than the sum of its proper divisors (71632821).

129999891 is an equidigital number, since it uses as much as digits as its factorization.

129999891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 884370 (or 884363 counting only the distinct ones).

The product of its digits is 944784, while the sum is 57.

The square root of 129999891 is about 11401.7494710242. The cubic root of 129999891 is about 506.5795603275.

The spelling of 129999891 in words is "one hundred twenty-nine million, nine hundred ninety-nine thousand, eight hundred ninety-one".