1321043665 has 4 divisors (see below), whose sum is σ = 1585252404. Its totient is φ = 1056834928.

The previous prime is 1321043639. The next prime is 1321043677. The reversal of 1321043665 is 5663401231.

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 726464209 + 594579456 = 26953^2 + 24384^2 .

It is a cyclic number.

It is not a de Polignac number, because 1321043665 - 2¹⁵ = 1321010897 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 132104362 + ... + 132104371.

It is an arithmetic number, because the mean of its divisors is an integer number (396313101).

Almost surely, 2^1321043665 is an apocalyptic number.

It is an amenable number.

1321043665 is a deficient number, since it is larger than the sum of its proper divisors (264208739).

1321043665 is an equidigital number, since it uses as much as digits as its factorization.

1321043665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 264208738.

The product of its (nonzero) digits is 12960, while the sum is 31.

The square root of 1321043665 is about 36346.1643781019. The cubic root of 1321043665 is about 1097.2503404180.

Adding to 1321043665 its reverse (5663401231), we get a palindrome (6984444896).

The spelling of 1321043665 in words is "one billion, three hundred twenty-one million, forty-three thousand, six hundred sixty-five".