1291766816891 has 4 divisors (see below), whose sum is σ = 1296533484384. Its totient is φ = 1287000149400.

The previous prime is 1291766816839. The next prime is 1291766816953. The reversal of 1291766816891 is 1986186671921.

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

It is a cyclic number.

It is not a de Polignac number, because 1291766816891 - 2¹⁴ = 1291766800507 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1291766896891) 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, 2383333340 + ... + 2383333881.

It is an arithmetic number, because the mean of its divisors is an integer number (324133371096).

Almost surely, 2^{1291766816891} is an apocalyptic number.

1291766816891 is a deficient number, since it is larger than the sum of its proper divisors (4766667493).

1291766816891 is an equidigital number, since it uses as much as digits as its factorization.

1291766816891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4766667492.

The product of its digits is 15676416, while the sum is 65.

The spelling of 1291766816891 in words is "one trillion, two hundred ninety-one billion, seven hundred sixty-six million, eight hundred sixteen thousand, eight hundred ninety-one".