669491591 has 2 divisors, whose sum is σ = 669491592. Its totient is φ = 669491590.

The previous prime is 669491539. The next prime is 669491609. The reversal of 669491591 is 195194966.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 669491591 - 2⁶ = 669491527 is a prime.

It is a super-2 number, since 2×669491591² = 896437980839422562, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (669491791) 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, 334745795 + 334745796.

It is an arithmetic number, because the mean of its divisors is an integer number (334745796).

Almost surely, 2^669491591 is an apocalyptic number.

669491591 is a deficient number, since it is larger than the sum of its proper divisors (1).

669491591 is an equidigital number, since it uses as much as digits as its factorization.

669491591 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 524880, while the sum is 50.

The square root of 669491591 is about 25874.5355707112. The cubic root of 669491591 is about 874.8126253474.

The spelling of 669491591 in words is "six hundred sixty-nine million, four hundred ninety-one thousand, five hundred ninety-one".