6181991 has 4 divisors (see below), whose sum is σ = 6190800. Its totient is φ = 6173184.

The previous prime is 6181969. The next prime is 6181993. The reversal of 6181991 is 1991816.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-6181991 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 (6181993) 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, 3251 + ... + 4788.

It is an arithmetic number, because the mean of its divisors is an integer number (1547700).

Almost surely, 2^6181991 is an apocalyptic number.

6181991 is a deficient number, since it is larger than the sum of its proper divisors (8809).

6181991 is an equidigital number, since it uses as much as digits as its factorization.

6181991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8808.

The product of its digits is 3888, while the sum is 35.

The square root of 6181991 is about 2486.3609955113. The cubic root of 6181991 is about 183.5310106549.

The spelling of 6181991 in words is "six million, one hundred eighty-one thousand, nine hundred ninety-one".