642640 has 40 divisors (see below), whose sum is σ = 1551240. Its totient is φ = 247296.

The previous prime is 642623. The next prime is 642673. The reversal of 642640 is 46246.

It can be written as a sum of positive squares in 4 ways, for example, as 15376 + 627264 = 124^2 + 792^2 .

It is a tau number, because it is divible by the number of its divisors (40).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2182 + ... + 2458.

It is an arithmetic number, because the mean of its divisors is an integer number (38781).

2⁶⁴²⁶⁴⁰ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 642640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (775620).

642640 is an abundant number, since it is smaller than the sum of its proper divisors (908600).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

642640 is a wasteful number, since it uses less digits than its factorization.

642640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 319 (or 313 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 22.

The square root of 642640 is about 801.6483019380. The cubic root of 642640 is about 86.2957189525.

Adding to 642640 its reverse (46246), we get a palindrome (688886).

It can be divided in two parts, 64 and 2640, that added together give a square (2704 = 52²).

The spelling of 642640 in words is "six hundred forty-two thousand, six hundred forty".