66659639 has 2 divisors, whose sum is σ = 66659640. Its totient is φ = 66659638.

The previous prime is 66659623. The next prime is 66659653. The reversal of 66659639 is 93695666.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 66659639 - 2⁴ = 66659623 is a prime.

It is a super-2 number, since 2×66659639² = 8887014943220642, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66659689) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33329819 + 33329820.

It is an arithmetic number, because the mean of its divisors is an integer number (33329820).

Almost surely, 2^66659639 is an apocalyptic number.

66659639 is a deficient number, since it is larger than the sum of its proper divisors (1).

66659639 is an equidigital number, since it uses as much as digits as its factorization.

66659639 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1574640, while the sum is 50.

The square root of 66659639 is about 8164.5354429998. The cubic root of 66659639 is about 405.4658846415.

The spelling of 66659639 in words is "sixty-six million, six hundred fifty-nine thousand, six hundred thirty-nine".