640738 has 8 divisors (see below), whose sum is σ = 1098432. Its totient is φ = 274596.

The previous prime is 640733. The next prime is 640741. The reversal of 640738 is 837046.

640738 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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

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

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 22870 + ... + 22897.

It is an arithmetic number, because the mean of its divisors is an integer number (137304).

2⁶⁴⁰⁷³⁸ is an apocalyptic number.

640738 is a deficient number, since it is larger than the sum of its proper divisors (457694).

640738 is a wasteful number, since it uses less digits than its factorization.

640738 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 45776.

The product of its (nonzero) digits is 4032, while the sum is 28.

The square root of 640738 is about 800.4611171069. The cubic root of 640738 is about 86.2104993106.

It can be divided in two parts, 640 and 738, that added together give a triangular number (1378 = T₅₂).

The spelling of 640738 in words is "six hundred forty thousand, seven hundred thirty-eight".