• 305 can be written using four 4's:

305 has 4 divisors (see below), whose sum is σ = 372. Its totient is φ = 240.

The previous prime is 293. The next prime is 307. The reversal of 305 is 503.

305 is nontrivially palindromic in base 4 and base 16.

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 49 + 256 = 7^2 + 16^2 .

It is not a de Polignac number, because 305 - 2^{6} = 241 is a prime.

It is a fibodiv number, since the Fibonacci-like sequence with seeds 30 and 5 contains 305 itself.

It is an alternating number because its digits alternate between odd and even.

It is a Duffinian number.

305 is an undulating number in base 16.

It is a plaindrome in base 6, base 9, base 11, base 14 and base 15.

It is a nialpdrome in base 5.

It is a junction number, because it is equal to *n*+sod(*n*) for *n* = 292 and 301.

It is not an unprimeable number, because it can be changed into a prime (307) 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, 26 + ... + 35.

It is an arithmetic number, because the mean of its divisors is an integer number (93).

It is an amenable number.

305 is a deficient number, since it is larger than the sum of its proper divisors (67).

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

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

The sum of its prime factors is 66.

The product of its (nonzero) digits is 15, while the sum is 8.

The square root of 305 is about 17.4642491966. The cubic root of 305 is about 6.7313154973.

Adding to 305 its reverse (503), we get a palindrome (808).

The spelling of 305 in words is "three hundred five", and thus it is an aban number and an oban number.

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