865537891 has 4 divisors (see below), whose sum is σ = 866246832. Its totient is φ = 864828952.

The previous prime is 865537877. The next prime is 865537901. The reversal of 865537891 is 198735568.

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

It is a cyclic number.

It is not a de Polignac number, because 865537891 - 2¹³ = 865529699 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (865537811) 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, 352636 + ... + 355081.

It is an arithmetic number, because the mean of its divisors is an integer number (216561708).

Almost surely, 2^865537891 is an apocalyptic number.

865537891 is a deficient number, since it is larger than the sum of its proper divisors (708941).

865537891 is a wasteful number, since it uses less digits than its factorization.

865537891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 708940.

The product of its digits is 1814400, while the sum is 52.

The square root of 865537891 is about 29420.0253398939. The cubic root of 865537891 is about 953.0054003416.

It can be divided in two parts, 865 and 537891, that added together give a square (538756 = 734²).

The spelling of 865537891 in words is "eight hundred sixty-five million, five hundred thirty-seven thousand, eight hundred ninety-one".