1991398129 has 8 divisors (see below), whose sum is σ = 2354362560. Its totient is φ = 1648053456.

The previous prime is 1991398103. The next prime is 1991398147. The reversal of 1991398129 is 9218931991.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 1991398129 - 2¹¹ = 1991396081 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1991398169) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4904719 + ... + 4905124.

It is an arithmetic number, because the mean of its divisors is an integer number (294295320).

Almost surely, 2^1991398129 is an apocalyptic number.

It is an amenable number.

1991398129 is a deficient number, since it is larger than the sum of its proper divisors (362964431).

1991398129 is an equidigital number, since it uses as much as digits as its factorization.

1991398129 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9809879.

The product of its digits is 314928, while the sum is 52.

The square root of 1991398129 is about 44625.0840783522. The cubic root of 1991398129 is about 1258.1121744018.

The spelling of 1991398129 in words is "one billion, nine hundred ninety-one million, three hundred ninety-eight thousand, one hundred twenty-nine".