1265645663 has 4 divisors (see below), whose sum is σ = 1270688328. Its totient is φ = 1260603000.

The previous prime is 1265645659. The next prime is 1265645701. The reversal of 1265645663 is 3665465621.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 3665465621 = 79 ⋅46398299.

It is a cyclic number.

It is not a de Polignac number, because 1265645663 - 2² = 1265645659 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 (1265645063) 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, 2520956 + ... + 2521457.

It is an arithmetic number, because the mean of its divisors is an integer number (317672082).

Almost surely, 2^1265645663 is an apocalyptic number.

1265645663 is a deficient number, since it is larger than the sum of its proper divisors (5042665).

1265645663 is an equidigital number, since it uses as much as digits as its factorization.

1265645663 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5042664.

The product of its digits is 777600, while the sum is 44.

The square root of 1265645663 is about 35575.9140852347. The cubic root of 1265645663 is about 1081.6930643559.

The spelling of 1265645663 in words is "one billion, two hundred sixty-five million, six hundred forty-five thousand, six hundred sixty-three".