640730 has 16 divisors (see below), whose sum is σ = 1221480. Its totient is φ = 241152.

The previous prime is 640727. The next prime is 640733. The reversal of 640730 is 37046.

It is an interprime number because it is at equal distance from previous prime (640727) and next prime (640733).

It can be written as a sum of positive squares in 4 ways, for example, as 628849 + 11881 = 793^2 + 109^2 .

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, 1715 + ... + 2054.

2⁶⁴⁰⁷³⁰ is an apocalyptic number.

640730 is a deficient number, since it is larger than the sum of its proper divisors (580750).

640730 is a wasteful number, since it uses less digits than its factorization.

640730 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3793.

The product of its (nonzero) digits is 504, while the sum is 20.

The square root of 640730 is about 800.4561199716. The cubic root of 640730 is about 86.2101405124.

Adding to 640730 its reverse (37046), we get a palindrome (677776).

The spelling of 640730 in words is "six hundred forty thousand, seven hundred thirty".