6661649 has 2 divisors, whose sum is σ = 6661650. Its totient is φ = 6661648.

The previous prime is 6661643. The next prime is 6661661. The reversal of 6661649 is 9461666.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 3972049 + 2689600 = 1993^2 + 1640^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-6661649 is a prime.

It is a super-3 number, since 3×6661649³ (a number of 21 digits) contains 333 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (6661643) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3330824 + 3330825.

It is an arithmetic number, because the mean of its divisors is an integer number (3330825).

Almost surely, 2^6661649 is an apocalyptic number.

It is an amenable number.

6661649 is a deficient number, since it is larger than the sum of its proper divisors (1).

6661649 is an equidigital number, since it uses as much as digits as its factorization.

6661649 is an evil number, because the sum of its binary digits is even.

The product of its digits is 46656, while the sum is 38.

The square root of 6661649 is about 2581.0170475996. The cubic root of 6661649 is about 188.1599758739.

The spelling of 6661649 in words is "six million, six hundred sixty-one thousand, six hundred forty-nine".