640739 has 8 divisors (see below), whose sum is σ = 721920. Its totient is φ = 563400.

The previous prime is 640733. The next prime is 640741. The reversal of 640739 is 937046.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 640739 - 2⁸ = 640483 is a prime.

It is a super-2 number, since 2×640739² = 821092932242, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (640733) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 599 + ... + 1280.

It is an arithmetic number, because the mean of its divisors is an integer number (90240).

2⁶⁴⁰⁷³⁹ is an apocalyptic number.

640739 is a deficient number, since it is larger than the sum of its proper divisors (81181).

640739 is a wasteful number, since it uses less digits than its factorization.

640739 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1921.

The product of its (nonzero) digits is 4536, while the sum is 29.

The square root of 640739 is about 800.4617417466. The cubic root of 640739 is about 86.2105441601.

It can be divided in two parts, 6407 and 39, that added together give a palindrome (6446).

The spelling of 640739 in words is "six hundred forty thousand, seven hundred thirty-nine".