9855 has 16 divisors (see below), whose sum is σ = 17760. Its totient is φ = 5184.

The previous prime is 9851. The next prime is 9857. The reversal of 9855 is 5589.

It is not a de Polignac number, because 9855 - 2² = 9851 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a plaindrome in base 16.

It is a nialpdrome in base 10.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (9851) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 99 + ... + 171.

It is an arithmetic number, because the mean of its divisors is an integer number (1110).

It is the magic constant of a 27 × 27 magic square.

2⁹⁸⁵⁵ is an apocalyptic number.

9855 is a deficient number, since it is larger than the sum of its proper divisors (7905).

9855 is a wasteful number, since it uses less digits than its factorization.

9855 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 87 (or 81 counting only the distinct ones).

The product of its digits is 1800, while the sum is 27.

The square root of 9855 is about 99.2723526466. The cubic root of 9855 is about 21.4397084964.

Multiplying 9855 by its sum of digits (27), we get a triangular number (266085 = T₇₂₉).

It can be divided in two parts, 985 and 5, that added together give a triangular number (990 = T₄₄).

The spelling of 9855 in words is "nine thousand, eight hundred fifty-five".