1261050781 has 4 divisors (see below), whose sum is σ = 1267452252. Its totient is φ = 1254649312.

The previous prime is 1261050779. The next prime is 1261050793. The reversal of 1261050781 is 1870501621.

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

It can be written as a sum of positive squares in 2 ways, for example, as 1155660025 + 105390756 = 33995^2 + 10266^2 .

It is a cyclic number.

It is not a de Polignac number, because 1261050781 - 2¹ = 1261050779 is a prime.

It is a super-2 number, since 2×1261050781² = 3180498144521419922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1261050481) 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, 3200440 + ... + 3200833.

It is an arithmetic number, because the mean of its divisors is an integer number (316863063).

Almost surely, 2^1261050781 is an apocalyptic number.

It is an amenable number.

1261050781 is a deficient number, since it is larger than the sum of its proper divisors (6401471).

1261050781 is an equidigital number, since it uses as much as digits as its factorization.

1261050781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6401470.

The product of its (nonzero) digits is 3360, while the sum is 31.

The square root of 1261050781 is about 35511.2768145557. The cubic root of 1261050781 is about 1080.3824608507.

The spelling of 1261050781 in words is "one billion, two hundred sixty-one million, fifty thousand, seven hundred eighty-one".