660506921 has 2 divisors, whose sum is σ = 660506922. Its totient is φ = 660506920.

The previous prime is 660506909. The next prime is 660506927. The reversal of 660506921 is 129605066.

It is a happy number.

660506921 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., 459888025 + 200618896 = 21445^2 + 14164^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-660506921 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (660506927) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330253460 + 330253461.

It is an arithmetic number, because the mean of its divisors is an integer number (330253461).

Almost surely, 2^660506921 is an apocalyptic number.

It is an amenable number.

660506921 is a deficient number, since it is larger than the sum of its proper divisors (1).

660506921 is an equidigital number, since it uses as much as digits as its factorization.

660506921 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 19440, while the sum is 35.

The square root of 660506921 is about 25700.3292002262. The cubic root of 660506921 is about 870.8816187467.

The spelling of 660506921 in words is "six hundred sixty million, five hundred six thousand, nine hundred twenty-one".