660057991 has 4 divisors (see below), whose sum is σ = 663513984. Its totient is φ = 656602000.

The previous prime is 660057971. The next prime is 660058027. The reversal of 660057991 is 199750066.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 199750066 = 2 ⋅99875033.

It is a cyclic number.

It is not a de Polignac number, because 660057991 - 2¹¹ = 660055943 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (660057901) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1727710 + ... + 1728091.

It is an arithmetic number, because the mean of its divisors is an integer number (165878496).

Almost surely, 2^660057991 is an apocalyptic number.

660057991 is a deficient number, since it is larger than the sum of its proper divisors (3455993).

660057991 is a wasteful number, since it uses less digits than its factorization.

660057991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3455992.

The product of its (nonzero) digits is 102060, while the sum is 43.

The square root of 660057991 is about 25691.5937808459. The cubic root of 660057991 is about 870.6842685588.

The spelling of 660057991 in words is "six hundred sixty million, fifty-seven thousand, nine hundred ninety-one".