1261305687 has 4 divisors (see below), whose sum is σ = 1681740920. Its totient is φ = 840870456.

The previous prime is 1261305679. The next prime is 1261305719. The reversal of 1261305687 is 7865031621.

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

It is not a de Polignac number, because 1261305687 - 2³ = 1261305679 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 (1261305637) 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, 210217612 + ... + 210217617.

It is an arithmetic number, because the mean of its divisors is an integer number (420435230).

Almost surely, 2^1261305687 is an apocalyptic number.

1261305687 is a deficient number, since it is larger than the sum of its proper divisors (420435233).

1261305687 is an equidigital number, since it uses as much as digits as its factorization.

1261305687 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 420435232.

The product of its (nonzero) digits is 60480, while the sum is 39.

The square root of 1261305687 is about 35514.8657184565. The cubic root of 1261305687 is about 1080.4552513156.

The spelling of 1261305687 in words is "one billion, two hundred sixty-one million, three hundred five thousand, six hundred eighty-seven".