1565 has 4 divisors (see below), whose sum is σ = 1884.
Its totient is φ = 1248.
The previous prime is 1559. The next prime is 1567. The reversal of 1565 is 5651.
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 196 + 1369 = 14^2 + 37^2
It is a cyclic number.
It is not a de Polignac number, because 1565 - 24 = 1549 is a prime.
It is a Duffinian number.
It is a plaindrome in base 6.
It is a nialpdrome in base 12.
It is a congruent number.
It is not an unprimeable number, because it can be changed into a prime (1567) 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, 152 + ... + 161.
It is an arithmetic number, because the mean of its divisors is an integer number (471).
21565 is an apocalyptic number.
It is an amenable number.
1565 is a deficient number, since it is larger than the sum of its proper divisors (319).
1565 is an equidigital number, since it uses as much as digits as its factorization.
1565 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 318.
The product of its digits is 150, while the sum is 17.
The square root of 1565 is about 39.5600808897.
The cubic root of 1565 is about 11.6101575714.
It can be divided in two parts, 156 and 5, that multiplied together give a triangular number (780 = T39).
The spelling of 1565 in words is "one thousand, five hundred sixty-five".