861291 has 12 divisors (see below), whose sum is σ = 1260168. Its totient is φ = 566784.

The previous prime is 861239. The next prime is 861293. The reversal of 861291 is 192168.

861291 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 861291 - 2⁷ = 861163 is a prime.

It is a Smith number, since the sum of its digits (27) coincides with the sum of the digits of its prime factors.

It is not an unprimeable number, because it can be changed into a prime (861293) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 171 + ... + 1323.

It is an arithmetic number, because the mean of its divisors is an integer number (105014).

2⁸⁶¹²⁹¹ is an apocalyptic number.

861291 is a deficient number, since it is larger than the sum of its proper divisors (398877).

861291 is a wasteful number, since it uses less digits than its factorization.

861291 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1242 (or 1239 counting only the distinct ones).

The product of its digits is 864, while the sum is 27.

The square root of 861291 is about 928.0576490714. The cubic root of 861291 is about 95.1444156256.

The spelling of 861291 in words is "eight hundred sixty-one thousand, two hundred ninety-one".