861905591 has 2 divisors, whose sum is σ = 861905592. Its totient is φ = 861905590.

The previous prime is 861905543. The next prime is 861905609. The reversal of 861905591 is 195509168.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 861905591 - 2¹⁴ = 861889207 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (861901591) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 430952795 + 430952796.

It is an arithmetic number, because the mean of its divisors is an integer number (430952796).

Almost surely, 2^861905591 is an apocalyptic number.

861905591 is a deficient number, since it is larger than the sum of its proper divisors (1).

861905591 is an equidigital number, since it uses as much as digits as its factorization.

861905591 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 97200, while the sum is 44.

The square root of 861905591 is about 29358.2286761310. The cubic root of 861905591 is about 951.6704096304.

The spelling of 861905591 in words is "eight hundred sixty-one million, nine hundred five thousand, five hundred ninety-one".