1691055809 has 2 divisors, whose sum is σ = 1691055810. Its totient is φ = 1691055808.

The previous prime is 1691055761. The next prime is 1691055823. The reversal of 1691055809 is 9085501961.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1656245809 + 34810000 = 40697^2 + 5900^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1691055809 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 1691055809.

It is not a weakly prime, because it can be changed into another prime (1691055829) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 845527904 + 845527905.

It is an arithmetic number, because the mean of its divisors is an integer number (845527905).

Almost surely, 2^1691055809 is an apocalyptic number.

It is an amenable number.

1691055809 is a deficient number, since it is larger than the sum of its proper divisors (1).

1691055809 is an equidigital number, since it uses as much as digits as its factorization.

1691055809 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 97200, while the sum is 44.

The square root of 1691055809 is about 41122.4489664709. The cubic root of 1691055809 is about 1191.3864237895.

The spelling of 1691055809 in words is "one billion, six hundred ninety-one million, fifty-five thousand, eight hundred nine".