640026 has 36 divisors (see below), whose sum is σ = 1471626. Its totient is φ = 200880.

The previous prime is 640019. The next prime is 640027. The reversal of 640026 is 620046.

640026 is a `hidden beast` number, since 640 + 0 + 26 = 666.

It can be written as a sum of positive squares in only one way, i.e., 423801 + 216225 = 651^2 + 465^2 .

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a nialpdrome in base 15.

It is a junction number, because it is equal to n+sod(n) for n = 639990 and 640008.

It is not an unprimeable number, because it can be changed into a prime (640027) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 17280 + ... + 17316.

2⁶⁴⁰⁰²⁶ is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 640026, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (735813).

640026 is an abundant number, since it is smaller than the sum of its proper divisors (831600).

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

640026 is a wasteful number, since it uses less digits than its factorization.

640026 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 107 (or 73 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 18.

The square root of 640026 is about 800.0162498350. The cubic root of 640026 is about 86.1785545709.

The spelling of 640026 in words is "six hundred forty thousand, twenty-six".