661166609 has 2 divisors, whose sum is σ = 661166610. Its totient is φ = 661166608.

The previous prime is 661166603. The next prime is 661166633. The reversal of 661166609 is 906661166.

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., 643129600 + 18037009 = 25360^2 + 4247^2 .

It is a cyclic number.

It is not a de Polignac number, because 661166609 - 2⁸ = 661166353 is a prime.

It is not a weakly prime, because it can be changed into another prime (661166603) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330583304 + 330583305.

It is an arithmetic number, because the mean of its divisors is an integer number (330583305).

Almost surely, 2^661166609 is an apocalyptic number.

It is an amenable number.

661166609 is a deficient number, since it is larger than the sum of its proper divisors (1).

661166609 is an equidigital number, since it uses as much as digits as its factorization.

661166609 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 69984, while the sum is 41.

The square root of 661166609 is about 25713.1602297345. The cubic root of 661166609 is about 871.1714562312.

The spelling of 661166609 in words is "six hundred sixty-one million, one hundred sixty-six thousand, six hundred nine".