1765665661 has 2 divisors, whose sum is σ = 1765665662. Its totient is φ = 1765665660.

The previous prime is 1765665659. The next prime is 1765665677. The reversal of 1765665661 is 1665665671.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1737639225 + 28026436 = 41685^2 + 5294^2 .

It is an emirp because it is prime and its reverse (1665665671) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1765665661 - 2¹ = 1765665659 is a prime.

Together with 1765665659, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1765665631) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 882832830 + 882832831.

It is an arithmetic number, because the mean of its divisors is an integer number (882832831).

Almost surely, 2^1765665661 is an apocalyptic number.

It is an amenable number.

1765665661 is a deficient number, since it is larger than the sum of its proper divisors (1).

1765665661 is an equidigital number, since it uses as much as digits as its factorization.

1765665661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1360800, while the sum is 49.

The square root of 1765665661 is about 42019.8246188629. The cubic root of 1765665661 is about 1208.6563097805.

The spelling of 1765665661 in words is "one billion, seven hundred sixty-five million, six hundred sixty-five thousand, six hundred sixty-one".