661009 has 2 divisors, whose sum is σ = 661010. Its totient is φ = 661008.

The previous prime is 660983. The next prime is 661019. The reversal of 661009 is 900166.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 595984 + 65025 = 772^2 + 255^2 .

It is a cyclic number.

It is not a de Polignac number, because 661009 - 2¹¹ = 658961 is a prime.

661009 is a lucky number.

It is not a weakly prime, because it can be changed into another prime (661019) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330504 + 330505.

It is an arithmetic number, because the mean of its divisors is an integer number (330505).

2⁶⁶¹⁰⁰⁹ is an apocalyptic number.

It is an amenable number.

661009 is a deficient number, since it is larger than the sum of its proper divisors (1).

661009 is an equidigital number, since it uses as much as digits as its factorization.

661009 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 324, while the sum is 22.

The square root of 661009 is about 813.0245998738. The cubic root of 661009 is about 87.1102227400.

The spelling of 661009 in words is "six hundred sixty-one thousand, nine".