667308721 has 2 divisors, whose sum is σ = 667308722. Its totient is φ = 667308720.

The previous prime is 667308689. The next prime is 667308737. The reversal of 667308721 is 127803766.

667308721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 385572496 + 281736225 = 19636^2 + 16785^2 .

It is a cyclic number.

It is not a de Polignac number, because 667308721 - 2⁵ = 667308689 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (667308121) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333654360 + 333654361.

It is an arithmetic number, because the mean of its divisors is an integer number (333654361).

Almost surely, 2^667308721 is an apocalyptic number.

It is an amenable number.

667308721 is a deficient number, since it is larger than the sum of its proper divisors (1).

667308721 is an equidigital number, since it uses as much as digits as its factorization.

667308721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 84672, while the sum is 40.

The square root of 667308721 is about 25832.3193112814. The cubic root of 667308721 is about 873.8608178160.

The spelling of 667308721 in words is "six hundred sixty-seven million, three hundred eight thousand, seven hundred twenty-one".