1691381599891 has 2 divisors, whose sum is σ = 1691381599892. Its totient is φ = 1691381599890.

The previous prime is 1691381599889. The next prime is 1691381599909. The reversal of 1691381599891 is 1989951831961.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 1691381599891 - 2¹ = 1691381599889 is a prime.

It is a super-2 number, since 2×1691381599891² (a number of 25 digits) contains 22 as substring.

Together with 1691381599889, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 1691381599891.

It is not a weakly prime, because it can be changed into another prime (1691381599091) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 845690799945 + 845690799946.

It is an arithmetic number, because the mean of its divisors is an integer number (845690799946).

Almost surely, 2^{1691381599891} is an apocalyptic number.

1691381599891 is a deficient number, since it is larger than the sum of its proper divisors (1).

1691381599891 is an equidigital number, since it uses as much as digits as its factorization.

1691381599891 is an evil number, because the sum of its binary digits is even.

The product of its digits is 37791360, while the sum is 70.

The spelling of 1691381599891 in words is "one trillion, six hundred ninety-one billion, three hundred eighty-one million, five hundred ninety-nine thousand, eight hundred ninety-one".