1265561663 has 4 divisors (see below), whose sum is σ = 1267393848. Its totient is φ = 1263729480.

The previous prime is 1265561641. The next prime is 1265561677. The reversal of 1265561663 is 3661655621.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 1265561663 - 2¹⁴ = 1265545279 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1265561663.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1265560663) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 915056 + ... + 916437.

It is an arithmetic number, because the mean of its divisors is an integer number (316848462).

Almost surely, 2^1265561663 is an apocalyptic number.

1265561663 is a deficient number, since it is larger than the sum of its proper divisors (1832185).

1265561663 is an equidigital number, since it uses as much as digits as its factorization.

1265561663 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1832184.

The product of its digits is 194400, while the sum is 41.

The square root of 1265561663 is about 35574.7334916230. The cubic root of 1265561663 is about 1081.6691334274.

The spelling of 1265561663 in words is "one billion, two hundred sixty-five million, five hundred sixty-one thousand, six hundred sixty-three".