16291991 has 4 divisors (see below), whose sum is σ = 16382184. Its totient is φ = 16201800.

The previous prime is 16291937. The next prime is 16291993. The reversal of 16291991 is 19919261.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 19919261 = 197 ⋅101113.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-16291991 is a prime.

It is a Duffinian number.

16291991 is a modest number, since divided by 1991 gives 1629 as remainder.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16291993) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 44825 + ... + 45186.

It is an arithmetic number, because the mean of its divisors is an integer number (4095546).

Almost surely, 2^16291991 is an apocalyptic number.

16291991 is a deficient number, since it is larger than the sum of its proper divisors (90193).

16291991 is an equidigital number, since it uses as much as digits as its factorization.

16291991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 90192.

The product of its digits is 8748, while the sum is 38.

The square root of 16291991 is about 4036.3338563602. Note that the first 3 decimals coincide. The cubic root of 16291991 is about 253.5078354882.

The spelling of 16291991 in words is "sixteen million, two hundred ninety-one thousand, nine hundred ninety-one".