815891 has 2 divisors, whose sum is σ = 815892. Its totient is φ = 815890.

The previous prime is 815869. The next prime is 815897. The reversal of 815891 is 198518.

It is a happy number.

815891 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 815891 - 2¹⁴ = 799507 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (815897) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 407945 + 407946.

It is an arithmetic number, because the mean of its divisors is an integer number (407946).

2⁸¹⁵⁸⁹¹ is an apocalyptic number.

815891 is a deficient number, since it is larger than the sum of its proper divisors (1).

815891 is an equidigital number, since it uses as much as digits as its factorization.

815891 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2880, while the sum is 32.

The square root of 815891 is about 903.2668487219. The cubic root of 815891 is about 93.4424135662.

The spelling of 815891 in words is "eight hundred fifteen thousand, eight hundred ninety-one".