861043991 has 4 divisors (see below), whose sum is σ = 861102984. Its totient is φ = 860985000.

The previous prime is 861043987. The next prime is 861044011. The reversal of 861043991 is 199340168.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 861043991 - 2² = 861043987 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 (861043921) 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 3 ways as a sum of consecutive naturals, for example, 10256 + ... + 42746.

It is an arithmetic number, because the mean of its divisors is an integer number (215275746).

Almost surely, 2^861043991 is an apocalyptic number.

861043991 is a deficient number, since it is larger than the sum of its proper divisors (58993).

861043991 is a wasteful number, since it uses less digits than its factorization.

861043991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 58992.

The product of its (nonzero) digits is 46656, while the sum is 41.

The square root of 861043991 is about 29343.5510973025. The cubic root of 861043991 is about 951.3531929081.

The spelling of 861043991 in words is "eight hundred sixty-one million, forty-three thousand, nine hundred ninety-one".