1686661 has 2 divisors, whose sum is σ = 1686662. Its totient is φ = 1686660.

The previous prime is 1686647. The next prime is 1686667. The reversal of 1686661 is 1666861.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1600225 + 86436 = 1265^2 + 294^2 .

It is a cyclic number.

It is not a de Polignac number, because 1686661 - 2⁹ = 1686149 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1686667) 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, 843330 + 843331.

It is an arithmetic number, because the mean of its divisors is an integer number (843331).

2^1686661 is an apocalyptic number.

It is an amenable number.

1686661 is a deficient number, since it is larger than the sum of its proper divisors (1).

1686661 is an equidigital number, since it uses as much as digits as its factorization.

1686661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 10368, while the sum is 34.

The square root of 1686661 is about 1298.7151342770. The cubic root of 1686661 is about 119.0353448196.

The spelling of 1686661 in words is "one million, six hundred eighty-six thousand, six hundred sixty-one".