1561305965 has 4 divisors (see below), whose sum is σ = 1873567164. Its totient is φ = 1249044768.

The previous prime is 1561305961. The next prime is 1561305989. The reversal of 1561305965 is 5695031651.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 5695031651 = 41 ⋅138903211.

It can be written as a sum of positive squares in 2 ways, for example, as 901740841 + 659565124 = 30029^2 + 25682^2 .

It is a cyclic number.

It is not a de Polignac number, because 1561305965 - 2² = 1561305961 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1561305961) 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, 156130592 + ... + 156130601.

It is an arithmetic number, because the mean of its divisors is an integer number (468391791).

Almost surely, 2^1561305965 is an apocalyptic number.

It is an amenable number.

1561305965 is a deficient number, since it is larger than the sum of its proper divisors (312261199).

1561305965 is an equidigital number, since it uses as much as digits as its factorization.

1561305965 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 312261198.

The product of its (nonzero) digits is 121500, while the sum is 41.

The square root of 1561305965 is about 39513.3643847243. The cubic root of 1561305965 is about 1160.1015480364.

The spelling of 1561305965 in words is "one billion, five hundred sixty-one million, three hundred five thousand, nine hundred sixty-five".