1261257805 has 8 divisors (see below), whose sum is σ = 1514955744. Its totient is φ = 1008042000.

The previous prime is 1261257799. The next prime is 1261257817. The reversal of 1261257805 is 5087521621.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 1261257805 - 2¹⁵ = 1261225037 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 114751 + ... + 125260.

It is an arithmetic number, because the mean of its divisors is an integer number (189369468).

Almost surely, 2^1261257805 is an apocalyptic number.

It is an amenable number.

1261257805 is a deficient number, since it is larger than the sum of its proper divisors (253697939).

1261257805 is a wasteful number, since it uses less digits than its factorization.

1261257805 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 241067.

The product of its (nonzero) digits is 33600, while the sum is 37.

The square root of 1261257805 is about 35514.1915999787. The cubic root of 1261257805 is about 1080.4415789723.

The spelling of 1261257805 in words is "one billion, two hundred sixty-one million, two hundred fifty-seven thousand, eight hundred five".