1265040661 has 4 divisors (see below), whose sum is σ = 1265539500. Its totient is φ = 1264541824.

The previous prime is 1265040659. The next prime is 1265040671. The reversal of 1265040661 is 1660405621.

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 810540900 + 454499761 = 28470^2 + 21319^2 .

It is a cyclic number.

It is not a de Polignac number, because 1265040661 - 2¹ = 1265040659 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 (1265040611) 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, 245596 + ... + 250693.

It is an arithmetic number, because the mean of its divisors is an integer number (316384875).

Almost surely, 2^1265040661 is an apocalyptic number.

It is an amenable number.

1265040661 is a deficient number, since it is larger than the sum of its proper divisors (498839).

1265040661 is an equidigital number, since it uses as much as digits as its factorization.

1265040661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 498838.

The product of its (nonzero) digits is 8640, while the sum is 31.

The square root of 1265040661 is about 35567.4100968850. The cubic root of 1265040661 is about 1081.5206804652.

The spelling of 1265040661 in words is "one billion, two hundred sixty-five million, forty thousand, six hundred sixty-one".