667561 has 2 divisors, whose sum is σ = 667562. Its totient is φ = 667560.

The previous prime is 667559. The next prime is 667577. The reversal of 667561 is 165766.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 609961 + 57600 = 781^2 + 240^2 .

It is a cyclic number.

It is not a de Polignac number, because 667561 - 2¹ = 667559 is a prime.

Together with 667559, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (667501) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333780 + 333781.

It is an arithmetic number, because the mean of its divisors is an integer number (333781).

2⁶⁶⁷⁵⁶¹ is an apocalyptic number.

It is an amenable number.

667561 is a deficient number, since it is larger than the sum of its proper divisors (1).

667561 is an equidigital number, since it uses as much as digits as its factorization.

667561 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 7560, while the sum is 31.

The square root of 667561 is about 817.0440624593. The cubic root of 667561 is about 87.3970926251.

The spelling of 667561 in words is "six hundred sixty-seven thousand, five hundred sixty-one".