1261666255 has 4 divisors (see below), whose sum is σ = 1513999512. Its totient is φ = 1009333000.

The previous prime is 1261666247. The next prime is 1261666277. The reversal of 1261666255 is 5526661621.

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

It is not a de Polignac number, because 1261666255 - 2³ = 1261666247 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 3 ways as a sum of consecutive naturals, for example, 126166621 + ... + 126166630.

It is an arithmetic number, because the mean of its divisors is an integer number (378499878).

Almost surely, 2^1261666255 is an apocalyptic number.

1261666255 is a deficient number, since it is larger than the sum of its proper divisors (252333257).

1261666255 is an equidigital number, since it uses as much as digits as its factorization.

1261666255 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 252333256.

The product of its digits is 129600, while the sum is 40.

The square root of 1261666255 is about 35519.9416525422. The cubic root of 1261666255 is about 1080.5581976714.

The spelling of 1261666255 in words is "one billion, two hundred sixty-one million, six hundred sixty-six thousand, two hundred fifty-five".