660640639 has 4 divisors (see below), whose sum is σ = 660731680. Its totient is φ = 660549600.

The previous prime is 660640637. The next prime is 660640709. The reversal of 660640639 is 936046066.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 660640639 - 2¹ = 660640637 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 (660640637) 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 in 3 ways as a sum of consecutive naturals, for example, 33594 + ... + 49495.

It is an arithmetic number, because the mean of its divisors is an integer number (165182920).

Almost surely, 2^660640639 is an apocalyptic number.

660640639 is a deficient number, since it is larger than the sum of its proper divisors (91041).

660640639 is an equidigital number, since it uses as much as digits as its factorization.

660640639 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 91040.

The product of its (nonzero) digits is 139968, while the sum is 40.

The square root of 660640639 is about 25702.9305527599. The cubic root of 660640639 is about 870.9403840611.

The spelling of 660640639 in words is "six hundred sixty million, six hundred forty thousand, six hundred thirty-nine".