1261444819861 has 4 divisors (see below), whose sum is σ = 1262262348832. Its totient is φ = 1260627290892.

The previous prime is 1261444819847. The next prime is 1261444819867. The reversal of 1261444819861 is 1689184441621.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 1261444819861 - 2³⁵ = 1227085081493 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 (1261444819867) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 408762171 + ... + 408765256.

It is an arithmetic number, because the mean of its divisors is an integer number (315565587208).

Almost surely, 2^{1261444819861} is an apocalyptic number.

It is an amenable number.

1261444819861 is a deficient number, since it is larger than the sum of its proper divisors (817528971).

1261444819861 is an equidigital number, since it uses as much as digits as its factorization.

1261444819861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 817528970.

The product of its digits is 2654208, while the sum is 55.

The spelling of 1261444819861 in words is "one trillion, two hundred sixty-one billion, four hundred forty-four million, eight hundred nineteen thousand, eight hundred sixty-one".