668549989 has 2 divisors, whose sum is σ = 668549990. Its totient is φ = 668549988.

The previous prime is 668549983. The next prime is 668550011. The reversal of 668549989 is 989945866.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 343360900 + 325189089 = 18530^2 + 18033^2 .

It is a cyclic number.

It is not a de Polignac number, because 668549989 - 2⁹ = 668549477 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 668549989.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (668549983) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 334274994 + 334274995.

It is an arithmetic number, because the mean of its divisors is an integer number (334274995).

Almost surely, 2^668549989 is an apocalyptic number.

It is an amenable number.

668549989 is a deficient number, since it is larger than the sum of its proper divisors (1).

668549989 is an equidigital number, since it uses as much as digits as its factorization.

668549989 is an evil number, because the sum of its binary digits is even.

The product of its digits is 33592320, while the sum is 64.

The square root of 668549989 is about 25856.3336341408. Note that the first 3 decimals coincide. The cubic root of 668549989 is about 874.4023081230.

The spelling of 668549989 in words is "six hundred sixty-eight million, five hundred forty-nine thousand, nine hundred eighty-nine".