660881509 has 2 divisors, whose sum is σ = 660881510. Its totient is φ = 660881508.

The previous prime is 660881461. The next prime is 660881513. The reversal of 660881509 is 905188066.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 643890625 + 16990884 = 25375^2 + 4122^2 .

It is a cyclic number.

It is not a de Polignac number, because 660881509 - 2¹⁹ = 660357221 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (660881519) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330440754 + 330440755.

It is an arithmetic number, because the mean of its divisors is an integer number (330440755).

Almost surely, 2^660881509 is an apocalyptic number.

It is an amenable number.

660881509 is a deficient number, since it is larger than the sum of its proper divisors (1).

660881509 is an equidigital number, since it uses as much as digits as its factorization.

660881509 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 103680, while the sum is 43.

The square root of 660881509 is about 25707.6157782086. The cubic root of 660881509 is about 871.0462196735.

The spelling of 660881509 in words is "six hundred sixty million, eight hundred eighty-one thousand, five hundred nine".