1665648581 has 2 divisors, whose sum is σ = 1665648582. Its totient is φ = 1665648580.

The previous prime is 1665648577. The next prime is 1665648587. The reversal of 1665648581 is 1858465661.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1194324481 + 471324100 = 34559^2 + 21710^2 .

It is a cyclic number.

It is not a de Polignac number, because 1665648581 - 2² = 1665648577 is a prime.

It is a super-2 number, since 2×1665648581² = 5548770390774627122, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1665648587) 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, 832824290 + 832824291.

It is an arithmetic number, because the mean of its divisors is an integer number (832824291).

Almost surely, 2^1665648581 is an apocalyptic number.

It is an amenable number.

1665648581 is a deficient number, since it is larger than the sum of its proper divisors (1).

1665648581 is an equidigital number, since it uses as much as digits as its factorization.

1665648581 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1382400, while the sum is 50.

The square root of 1665648581 is about 40812.3581896464. The cubic root of 1665648581 is about 1185.3896375177.

The spelling of 1665648581 in words is "one billion, six hundred sixty-five million, six hundred forty-eight thousand, five hundred eighty-one".