665618491 has 2 divisors, whose sum is σ = 665618492. Its totient is φ = 665618490.

The previous prime is 665618483. The next prime is 665618509. The reversal of 665618491 is 194816566.

665618491 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 665618491 - 2³ = 665618483 is a prime.

It is a super-2 number, since 2×665618491² = 886095951122234162, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (665618441) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332809245 + 332809246.

It is an arithmetic number, because the mean of its divisors is an integer number (332809246).

Almost surely, 2^665618491 is an apocalyptic number.

665618491 is a deficient number, since it is larger than the sum of its proper divisors (1).

665618491 is an equidigital number, since it uses as much as digits as its factorization.

665618491 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 311040, while the sum is 46.

The square root of 665618491 is about 25799.5831555473. The cubic root of 665618491 is about 873.1223916888.

The spelling of 665618491 in words is "six hundred sixty-five million, six hundred eighteen thousand, four hundred ninety-one".