668761909 has 2 divisors, whose sum is σ = 668761910. Its totient is φ = 668761908.

The previous prime is 668761901. The next prime is 668761927. The reversal of 668761909 is 909167866.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 462035025 + 206726884 = 21495^2 + 14378^2 .

It is a cyclic number.

It is not a de Polignac number, because 668761909 - 2³ = 668761901 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (668761901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 334380954 + 334380955.

It is an arithmetic number, because the mean of its divisors is an integer number (334380955).

Almost surely, 2^668761909 is an apocalyptic number.

It is an amenable number.

668761909 is a deficient number, since it is larger than the sum of its proper divisors (1).

668761909 is an equidigital number, since it uses as much as digits as its factorization.

668761909 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 979776, while the sum is 52.

The square root of 668761909 is about 25860.4313382434. The cubic root of 668761909 is about 874.4946890291.

The spelling of 668761909 in words is "six hundred sixty-eight million, seven hundred sixty-one thousand, nine hundred nine".