1605 has 8 divisors (see below), whose sum is σ = 2592. Its totient is φ = 848.

The previous prime is 1601. The next prime is 1607. The reversal of 1605 is 5061.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1605 - 2² = 1601 is a prime.

It is a plaindrome in base 6 and base 11.

It is a nialpdrome in base 13 and base 15.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 1605.

It is not an unprimeable number, because it can be changed into a prime (1601) 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 7 ways as a sum of consecutive naturals, for example, 39 + ... + 68.

It is an arithmetic number, because the mean of its divisors is an integer number (324).

1605 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

1605 is a deficient number, since it is larger than the sum of its proper divisors (987).

1605 is a wasteful number, since it uses less digits than its factorization.

1605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 115.

The product of its (nonzero) digits is 30, while the sum is 12.

The square root of 1605 is about 40.0624512480. The cubic root of 1605 is about 11.7082416910.

Adding to 1605 its reverse (5061), we get a palindrome (6666).

It can be divided in two parts, 1 and 605, that added together give a palindrome (606).

The spelling of 1605 in words is "one thousand, six hundred five".