1991395169 has 2 divisors, whose sum is σ = 1991395170. Its totient is φ = 1991395168.

The previous prime is 1991395163. The next prime is 1991395207. The reversal of 1991395169 is 9615931991.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1928351569 + 63043600 = 43913^2 + 7940^2 .

It is a cyclic number.

It is not a de Polignac number, because 1991395169 - 2¹⁶ = 1991329633 is a prime.

It is a super-2 number, since 2×1991395169² = 7931309438233077122, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 1991395169.

It is not a weakly prime, because it can be changed into another prime (1991395163) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 995697584 + 995697585.

It is an arithmetic number, because the mean of its divisors is an integer number (995697585).

Almost surely, 2^1991395169 is an apocalyptic number.

It is an amenable number.

1991395169 is a deficient number, since it is larger than the sum of its proper divisors (1).

1991395169 is an equidigital number, since it uses as much as digits as its factorization.

1991395169 is an evil number, because the sum of its binary digits is even.

The product of its digits is 590490, while the sum is 53.

The square root of 1991395169 is about 44625.0509131362. The cubic root of 1991395169 is about 1258.1115510518. Note that the first 3 decimals are identical.

The spelling of 1991395169 in words is "one billion, nine hundred ninety-one million, three hundred ninety-five thousand, one hundred sixty-nine".