640409140 has 48 divisors (see below), whose sum is σ = 1548086400. Its totient is φ = 217982592.

The previous prime is 640409111. The next prime is 640409141. The reversal of 640409140 is 41904046.

It is a Harshad number since it is a multiple of its sum of digits (28).

It is a junction number, because it is equal to n+sod(n) for n = 640409099 and 640409108.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640409141) 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, 3006 + ... + 35914.

It is an arithmetic number, because the mean of its divisors is an integer number (32251800).

Almost surely, 2^640409140 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 640409140, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (774043200).

640409140 is an abundant number, since it is smaller than the sum of its proper divisors (907677260).

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

640409140 is a wasteful number, since it uses less digits than its factorization.

640409140 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33064 (or 33062 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 28.

The square root of 640409140 is about 25306.3063286605. The cubic root of 640409140 is about 861.9574755213.

The spelling of 640409140 in words is "six hundred forty million, four hundred nine thousand, one hundred forty".