1261778871 has 4 divisors (see below), whose sum is σ = 1682371832. Its totient is φ = 841185912.

The previous prime is 1261778867. The next prime is 1261778927. The reversal of 1261778871 is 1788771621.

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

It is not a de Polignac number, because 1261778871 - 2² = 1261778867 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 1261778871.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1261778831) 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, 210296476 + ... + 210296481.

It is an arithmetic number, because the mean of its divisors is an integer number (420592958).

Almost surely, 2^1261778871 is an apocalyptic number.

1261778871 is a deficient number, since it is larger than the sum of its proper divisors (420592961).

1261778871 is an equidigital number, since it uses as much as digits as its factorization.

1261778871 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 420592960.

The product of its digits is 263424, while the sum is 48.

The square root of 1261778871 is about 35521.5268675208. The cubic root of 1261778871 is about 1080.5903468290.

The spelling of 1261778871 in words is "one billion, two hundred sixty-one million, seven hundred seventy-eight thousand, eight hundred seventy-one".