1261905965 has 4 divisors (see below), whose sum is σ = 1514287164. Its totient is φ = 1009524768.

The previous prime is 1261905949. The next prime is 1261905977. The reversal of 1261905965 is 5695091621.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 5695091621 = 58147 ⋅97943.

It can be written as a sum of positive squares in 2 ways, for example, as 531717481 + 730188484 = 23059^2 + 27022^2 .

It is a cyclic number.

It is not a de Polignac number, because 1261905965 - 2⁴ = 1261905949 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 126190592 + ... + 126190601.

It is an arithmetic number, because the mean of its divisors is an integer number (378571791).

Almost surely, 2^1261905965 is an apocalyptic number.

It is an amenable number.

1261905965 is a deficient number, since it is larger than the sum of its proper divisors (252381199).

1261905965 is an equidigital number, since it uses as much as digits as its factorization.

1261905965 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 252381198.

The product of its (nonzero) digits is 145800, while the sum is 44.

The square root of 1261905965 is about 35523.3157939965. The cubic root of 1261905965 is about 1080.6266268095.

It can be divided in two parts, 126 and 1905965, that added together give a palindrome (1906091).

The spelling of 1261905965 in words is "one billion, two hundred sixty-one million, nine hundred five thousand, nine hundred sixty-five".