1665964217 has 2 divisors, whose sum is σ = 1665964218. Its totient is φ = 1665964216.

The previous prime is 1665964159. The next prime is 1665964231. The reversal of 1665964217 is 7124695661.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 960318121 + 705646096 = 30989^2 + 26564^2 .

It is an emirp because it is prime and its reverse (7124695661) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1665964217 - 2¹⁶ = 1665898681 is a prime.

It is not a weakly prime, because it can be changed into another prime (1665960217) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 832982108 + 832982109.

It is an arithmetic number, because the mean of its divisors is an integer number (832982109).

Almost surely, 2^1665964217 is an apocalyptic number.

It is an amenable number.

1665964217 is a deficient number, since it is larger than the sum of its proper divisors (1).

1665964217 is an equidigital number, since it uses as much as digits as its factorization.

1665964217 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 544320, while the sum is 47.

The square root of 1665964217 is about 40816.2249234297. The cubic root of 1665964217 is about 1185.4645088555.

The spelling of 1665964217 in words is "one billion, six hundred sixty-five million, nine hundred sixty-four thousand, two hundred seventeen".