1665724909 has 2 divisors, whose sum is σ = 1665724910. Its totient is φ = 1665724908.

The previous prime is 1665724903. The next prime is 1665725051. The reversal of 1665724909 is 9094275661.

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., 1565784900 + 99940009 = 39570^2 + 9997^2 .

It is a cyclic number.

It is not a de Polignac number, because 1665724909 - 2³ = 1665724901 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1665724901) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 832862454 + 832862455.

It is an arithmetic number, because the mean of its divisors is an integer number (832862455).

Almost surely, 2^1665724909 is an apocalyptic number.

It is an amenable number.

1665724909 is a deficient number, since it is larger than the sum of its proper divisors (1).

1665724909 is an equidigital number, since it uses as much as digits as its factorization.

1665724909 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 816480, while the sum is 49.

The square root of 1665724909 is about 40813.2932878492. The cubic root of 1665724909 is about 1185.4077439857.

The spelling of 1665724909 in words is "one billion, six hundred sixty-five million, seven hundred twenty-four thousand, nine hundred nine".