66491599 has 2 divisors, whose sum is σ = 66491600. Its totient is φ = 66491598.

The previous prime is 66491591. The next prime is 66491609. The reversal of 66491599 is 99519466.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 66491599 - 2³ = 66491591 is a prime.

It is a super-2 number, since 2×66491599² = 8842265475153602, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66491591) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33245799 + 33245800.

It is an arithmetic number, because the mean of its divisors is an integer number (33245800).

Almost surely, 2^66491599 is an apocalyptic number.

66491599 is a deficient number, since it is larger than the sum of its proper divisors (1).

66491599 is an equidigital number, since it uses as much as digits as its factorization.

66491599 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 524880, while the sum is 49.

The square root of 66491599 is about 8154.2381005217. The cubic root of 66491599 is about 405.1248895945.

The spelling of 66491599 in words is "sixty-six million, four hundred ninety-one thousand, five hundred ninety-nine".