6661657 has 4 divisors (see below), whose sum is σ = 6727716. Its totient is φ = 6595600.

The previous prime is 6661649. The next prime is 6661661. The reversal of 6661657 is 7561666.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 5271616 + 1390041 = 2296^2 + 1179^2 .

It is a cyclic number.

It is not a de Polignac number, because 6661657 - 2³ = 6661649 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (6661687) 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 in 3 ways as a sum of consecutive naturals, for example, 32878 + ... + 33079.

It is an arithmetic number, because the mean of its divisors is an integer number (1681929).

Almost surely, 2^6661657 is an apocalyptic number.

It is an amenable number.

6661657 is a deficient number, since it is larger than the sum of its proper divisors (66059).

6661657 is a wasteful number, since it uses less digits than its factorization.

6661657 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 66058.

The product of its digits is 45360, while the sum is 37.

The square root of 6661657 is about 2581.0185973758. The cubic root of 6661657 is about 188.1600511945.

Subtracting 6661657 from its reverse (7561666), we obtain a palindrome (900009).

The spelling of 6661657 in words is "six million, six hundred sixty-one thousand, six hundred fifty-seven".