640420 has 48 divisors (see below), whose sum is σ = 1524096. Its totient is φ = 224000.

The previous prime is 640411. The next prime is 640421. The reversal of 640420 is 24046.

640420 = T₁₀₅ + T₁₀₆ + ... + T₁₇₀.

It is an Ulam number.

It is a junction number, because it is equal to n+sod(n) for n = 640394 and 640403.

It is not an unprimeable number, because it can be changed into a prime (640421) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8985 + ... + 9055.

It is an arithmetic number, because the mean of its divisors is an integer number (31752).

2⁶⁴⁰⁴²⁰ 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 640420, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (762048).

640420 is an abundant number, since it is smaller than the sum of its proper divisors (883676).

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

640420 is a wasteful number, since it uses less digits than its factorization.

640420 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 132 (or 130 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 16.

The square root of 640420 is about 800.2624569477. The cubic root of 640420 is about 86.1962347826.

Adding to 640420 its reverse (24046), we get a palindrome (664466).

The spelling of 640420 in words is "six hundred forty thousand, four hundred twenty".