1991117239 has 4 divisors (see below), whose sum is σ = 1991478960. Its totient is φ = 1990755520.

The previous prime is 1991117237. The next prime is 1991117251. The reversal of 1991117239 is 9327111991.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 9327111991 = 3581 ⋅2604611.

It is a cyclic number.

It is not a de Polignac number, because 1991117239 - 2¹ = 1991117237 is a prime.

It is a super-3 number, since 3×1991117239³ (a number of 29 digits) contains 333 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1991117195 and 1991117204.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1991117237) 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, 172474 + ... + 183655.

It is an arithmetic number, because the mean of its divisors is an integer number (497869740).

Almost surely, 2^1991117239 is an apocalyptic number.

1991117239 is a deficient number, since it is larger than the sum of its proper divisors (361721).

1991117239 is an equidigital number, since it uses as much as digits as its factorization.

1991117239 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 361720.

The product of its digits is 30618, while the sum is 43.

The square root of 1991117239 is about 44621.9367464031. The cubic root of 1991117239 is about 1258.0530186860.

The spelling of 1991117239 in words is "one billion, nine hundred ninety-one million, one hundred seventeen thousand, two hundred thirty-nine".