1605343661 has 2 divisors, whose sum is σ = 1605343662. Its totient is φ = 1605343660.

The previous prime is 1605343589. The next prime is 1605343709. The reversal of 1605343661 is 1663435061.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1551966025 + 53377636 = 39395^2 + 7306^2 .

It is an emirp because it is prime and its reverse (1663435061) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1605343661 - 2¹⁰ = 1605342637 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1605343261) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 802671830 + 802671831.

It is an arithmetic number, because the mean of its divisors is an integer number (802671831).

Almost surely, 2^1605343661 is an apocalyptic number.

It is an amenable number.

1605343661 is a deficient number, since it is larger than the sum of its proper divisors (1).

1605343661 is an equidigital number, since it uses as much as digits as its factorization.

1605343661 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 38880, while the sum is 35.

The square root of 1605343661 is about 40066.7400845140. The cubic root of 1605343661 is about 1170.9077283743.

The spelling of 1605343661 in words is "one billion, six hundred five million, three hundred forty-three thousand, six hundred sixty-one".