1265321809 has 2 divisors, whose sum is σ = 1265321810. Its totient is φ = 1265321808.

The previous prime is 1265321807. The next prime is 1265321843. The reversal of 1265321809 is 9081235621.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1165881025 + 99440784 = 34145^2 + 9972^2 .

It is a cyclic number.

It is not a de Polignac number, because 1265321809 - 2¹ = 1265321807 is a prime.

Together with 1265321807, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (1265321807) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 632660904 + 632660905.

It is an arithmetic number, because the mean of its divisors is an integer number (632660905).

Almost surely, 2^1265321809 is an apocalyptic number.

It is an amenable number.

1265321809 is a deficient number, since it is larger than the sum of its proper divisors (1).

1265321809 is an equidigital number, since it uses as much as digits as its factorization.

1265321809 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 25920, while the sum is 37.

The square root of 1265321809 is about 35571.3622033231. The cubic root of 1265321809 is about 1081.6007951109.

The spelling of 1265321809 in words is "one billion, two hundred sixty-five million, three hundred twenty-one thousand, eight hundred nine".