1605320891 has 2 divisors, whose sum is σ = 1605320892. Its totient is φ = 1605320890.

The previous prime is 1605320879. The next prime is 1605320917. The reversal of 1605320891 is 1980235061.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1605320891 is a prime.

It is not a weakly prime, because it can be changed into another prime (1605320851) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 802660445 + 802660446.

It is an arithmetic number, because the mean of its divisors is an integer number (802660446).

Almost surely, 2^1605320891 is an apocalyptic number.

1605320891 is a deficient number, since it is larger than the sum of its proper divisors (1).

1605320891 is an equidigital number, since it uses as much as digits as its factorization.

1605320891 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 12960, while the sum is 35.

The square root of 1605320891 is about 40066.4559326128. The cubic root of 1605320891 is about 1170.9021923436.

The spelling of 1605320891 in words is "one billion, six hundred five million, three hundred twenty thousand, eight hundred ninety-one".