891 has 10 divisors (see below), whose sum is σ = 1452. Its totient is φ = 540.

The previous prime is 887. The next prime is 907. The reversal of 891 is 198.

Added to its reverse (198) it gives a square (1089 = 33^{2}).

891 is nontrivially palindromic in base 2.

It is not a de Polignac number, because 891 - 2^{2} = 887 is a prime.

It is an Ulam number.

It is a plaindrome in base 14 and base 16.

It is a nialpdrome in base 11.

It is not an unprimeable number, because it can be changed into a prime (811) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 76 + ... + 86.

891 is a gapful number since it is divisible by the number (81) formed by its first and last digit.

891 is a deficient number, since it is larger than the sum of its proper divisors (561).

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

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

The sum of its prime factors is 23 (or 14 counting only the distinct ones).

The product of its digits is 72, while the sum is 18.

The square root of 891 is about 29.8496231132. The cubic root of 891 is about 9.6226029900.

Adding to 891 its sum of digits (18), we get a palindrome (909).

Adding to 891 its reverse (198), we get a square (1089 = 33^{2}).

It can be divided in two parts, 8 and 91, that added together give a palindrome (99).

The spelling of 891 in words is "eight hundred ninety-one", and thus it is an aban number.

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