1891791973409 has 4 divisors (see below), whose sum is σ = 2037314432916. Its totient is φ = 1746269513904.

The previous prime is 1891791973361. The next prime is 1891791973411. The reversal of 1891791973409 is 9043791971981.

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 1173625555600 + 718166417809 = 1083340^2 + 847447^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1891791973409 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1891791993409) 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, 72761229734 + ... + 72761229759.

It is an arithmetic number, because the mean of its divisors is an integer number (509328608229).

Almost surely, 2^{1891791973409} is an apocalyptic number.

It is an amenable number.

1891791973409 is a deficient number, since it is larger than the sum of its proper divisors (145522459507).

1891791973409 is a wasteful number, since it uses less digits than its factorization.

1891791973409 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 145522459506.

The product of its (nonzero) digits is 30862944, while the sum is 68.

The spelling of 1891791973409 in words is "one trillion, eight hundred ninety-one billion, seven hundred ninety-one million, nine hundred seventy-three thousand, four hundred nine".