1665600121 has 2 divisors, whose sum is σ = 1665600122. Its totient is φ = 1665600120.

The previous prime is 1665600067. The next prime is 1665600133. The reversal of 1665600121 is 1210065661.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1434894400 + 230705721 = 37880^2 + 15189^2 .

It is a cyclic number.

It is not a de Polignac number, because 1665600121 - 2¹¹ = 1665598073 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1665600121.

It is not a weakly prime, because it can be changed into another prime (1665600161) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 832800060 + 832800061.

It is an arithmetic number, because the mean of its divisors is an integer number (832800061).

Almost surely, 2^1665600121 is an apocalyptic number.

It is an amenable number.

1665600121 is a deficient number, since it is larger than the sum of its proper divisors (1).

1665600121 is an equidigital number, since it uses as much as digits as its factorization.

1665600121 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2160, while the sum is 28.

The square root of 1665600121 is about 40811.7644926068. The cubic root of 1665600121 is about 1185.3781415876.

Adding to 1665600121 its reverse (1210065661), we get a palindrome (2875665782).

The spelling of 1665600121 in words is "one billion, six hundred sixty-five million, six hundred thousand, one hundred twenty-one".