1660661 has 2 divisors, whose sum is σ = 1660662. Its totient is φ = 1660660.

The previous prime is 1660609. The next prime is 1660663.

1660661 is nontrivially palindromic in base 10.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1030225 + 630436 = 1015^2 + 794^2 .

It is a palprime.

It is a cyclic number.

It is not a de Polignac number, because 1660661 - 2¹⁸ = 1398517 is a prime.

It is a Sophie Germain prime.

Together with 1660663, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 1660661.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1660663) 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, 830330 + 830331.

It is an arithmetic number, because the mean of its divisors is an integer number (830331).

2^1660661 is an apocalyptic number.

It is an amenable number.

1660661 is a deficient number, since it is larger than the sum of its proper divisors (1).

1660661 is an equidigital number, since it uses as much as digits as its factorization.

1660661 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1296, while the sum is 26.

The square root of 1660661 is about 1288.6663648905. Note that the first 3 decimals coincide. The cubic root of 1660661 is about 118.4205286492.

The spelling of 1660661 in words is "one million, six hundred sixty thousand, six hundred sixty-one".