851 has 4 divisors (see below), whose sum is σ = 912. Its totient is φ = 792.

The previous prime is 839. The next prime is 853. The reversal of 851 is 158.

851 is nontrivially palindromic in base 16.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 158 = 2 ⋅79.

It is a cyclic number.

It is not a de Polignac number, because 851 - 2⁶ = 787 is a prime.

It is a Duffinian number.

851 is an undulating number in base 6 and base 16.

It is a plaindrome in base 9, base 12, base 14 and base 15.

It is a nialpdrome in base 10.

It is not an unprimeable number, because it can be changed into a prime (853) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5 + ... + 41.

It is an arithmetic number, because the mean of its divisors is an integer number (228).

851 is a deficient number, since it is larger than the sum of its proper divisors (61).

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

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

The sum of its prime factors is 60.

The product of its digits is 40, while the sum is 14.

The square root of 851 is about 29.1719042916. The cubic root of 851 is about 9.4763956934.

The spelling of 851 in words is "eight hundred fifty-one", and thus it is an aban number.