66356509 has 2 divisors, whose sum is σ = 66356510. Its totient is φ = 66356508.

The previous prime is 66356501. The next prime is 66356513. The reversal of 66356509 is 90565366.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 58216900 + 8139609 = 7630^2 + 2853^2 .

It is a cyclic number.

It is not a de Polignac number, because 66356509 - 2³ = 66356501 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66356501) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33178254 + 33178255.

It is an arithmetic number, because the mean of its divisors is an integer number (33178255).

Almost surely, 2^66356509 is an apocalyptic number.

It is an amenable number.

66356509 is a deficient number, since it is larger than the sum of its proper divisors (1).

66356509 is an equidigital number, since it uses as much as digits as its factorization.

66356509 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 145800, while the sum is 40.

The square root of 66356509 is about 8145.9504663360. The cubic root of 66356509 is about 404.8503414930.

The spelling of 66356509 in words is "sixty-six million, three hundred fifty-six thousand, five hundred nine".