851891 has 2 divisors, whose sum is σ = 851892. Its totient is φ = 851890.

The previous prime is 851881. The next prime is 851899. The reversal of 851891 is 198158.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-851891 is a prime.

It is a Sophie Germain prime.

It is not a weakly prime, because it can be changed into another prime (851899) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 425945 + 425946.

It is an arithmetic number, because the mean of its divisors is an integer number (425946).

2⁸⁵¹⁸⁹¹ is an apocalyptic number.

851891 is a deficient number, since it is larger than the sum of its proper divisors (1).

851891 is an equidigital number, since it uses as much as digits as its factorization.

851891 is an odious number, because the sum of its binary digits is odd.

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

The square root of 851891 is about 922.9794147217. The cubic root of 851891 is about 94.7970181310.

The spelling of 851891 in words is "eight hundred fifty-one thousand, eight hundred ninety-one".