861391 has 2 divisors, whose sum is σ = 861392. Its totient is φ = 861390.

The previous prime is 861361. The next prime is 861433. The reversal of 861391 is 193168.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-861391 is a prime.

861391 is a lucky number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (861361) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 430695 + 430696.

It is an arithmetic number, because the mean of its divisors is an integer number (430696).

2⁸⁶¹³⁹¹ is an apocalyptic number.

861391 is a deficient number, since it is larger than the sum of its proper divisors (1).

861391 is an equidigital number, since it uses as much as digits as its factorization.

861391 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1296, while the sum is 28.

The square root of 861391 is about 928.1115234712. Note that the first 3 decimals coincide. The cubic root of 861391 is about 95.1480977235.

The spelling of 861391 in words is "eight hundred sixty-one thousand, three hundred ninety-one".