905 has 4 divisors (see below), whose sum is σ = 1092. Its totient is φ = 720.
The previous prime is 887. The next prime is 907. The reversal of 905 is 509.
905 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.
It is a semiprime because it is the product of two primes.
It can be written as a sum of positive squares in 2 ways, for example, as 121 + 784 = 11^2 + 28^2 .
It is a de Polignac number, because none of the positive numbers 2k-905 is a prime.
It is an Ulam number.
It is an alternating number because its digits alternate between odd and even.
It is a Duffinian number.
It is a Curzon number.
It is a plaindrome in base 14 and base 16.
It is a nialpdrome in base 11.
It is a self number, because there is not a number n which added to its sum of digits gives 905.
It is a congruent number.
It is not an unprimeable number, because it can be changed into a prime (907) by changing a digit.
It is a pernicious number, because its binary representation contains a prime number (5) of ones.
It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 86 + ... + 95.
It is an arithmetic number, because the mean of its divisors is an integer number (273).
It is an amenable number.
905 is a deficient number, since it is larger than the sum of its proper divisors (187).
905 is a wasteful number, since it uses less digits than its factorization.
905 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 186.
The product of its (nonzero) digits is 45, while the sum is 14.
The square root of 905 is about 30.0832179130. The cubic root of 905 is about 9.6727402709.
Adding to 905 its sum of digits (14), we get a palindrome (919).
The spelling of 905 in words is "nine hundred five", and thus it is an aban number and an oban number.
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