1243645565 has 4 divisors (see below), whose sum is σ = 1492374684. Its totient is φ = 994916448.

The previous prime is 1243645549. The next prime is 1243645567. The reversal of 1243645565 is 5655463421.

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: 5655463421 = 53 ⋅106706857.

It can be written as a sum of positive squares in 2 ways, for example, as 400440121 + 843205444 = 20011^2 + 29038^2 .

It is a cyclic number.

It is not a de Polignac number, because 1243645565 - 2⁴ = 1243645549 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1243645567) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 124364552 + ... + 124364561.

It is an arithmetic number, because the mean of its divisors is an integer number (373093671).

Almost surely, 2^1243645565 is an apocalyptic number.

It is an amenable number.

1243645565 is a deficient number, since it is larger than the sum of its proper divisors (248729119).

1243645565 is an equidigital number, since it uses as much as digits as its factorization.

1243645565 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 248729118.

The product of its digits is 432000, while the sum is 41.

The square root of 1243645565 is about 35265.3592779090. The cubic root of 1243645565 is about 1075.3888811189.

The spelling of 1243645565 in words is "one billion, two hundred forty-three million, six hundred forty-five thousand, five hundred sixty-five".