666225509 has 2 divisors, whose sum is σ = 666225510. Its totient is φ = 666225508.

The previous prime is 666225467. The next prime is 666225559. The reversal of 666225509 is 905522666.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 521985409 + 144240100 = 22847^2 + 12010^2 .

It is a cyclic number.

It is not a de Polignac number, because 666225509 - 2²⁸ = 397790053 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (666225559) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333112754 + 333112755.

It is an arithmetic number, because the mean of its divisors is an integer number (333112755).

Almost surely, 2^666225509 is an apocalyptic number.

It is an amenable number.

666225509 is a deficient number, since it is larger than the sum of its proper divisors (1).

666225509 is an equidigital number, since it uses as much as digits as its factorization.

666225509 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 194400, while the sum is 41.

The square root of 666225509 is about 25811.3445794674. The cubic root of 666225509 is about 873.3877288569.

The spelling of 666225509 in words is "six hundred sixty-six million, two hundred twenty-five thousand, five hundred nine".