640938240 has 432 divisors, whose sum is σ = 2410611840. Its totient is φ = 156794880.

The previous prime is 640938227. The next prime is 640938247. The reversal of 640938240 is 42839046.

It is a happy number.

640938240 is a `hidden beast` number, since 6 + 409 + 3 + 8 + 240 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 640938195 and 640938204.

It is not an unprimeable number, because it can be changed into a prime (640938247) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 10863331 + ... + 10863389.

It is an arithmetic number, because the mean of its divisors is an integer number (5580120).

Almost surely, 2^640938240 is an apocalyptic number.

640938240 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 640938240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1205305920).

640938240 is an abundant number, since it is smaller than the sum of its proper divisors (1769673600).

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

640938240 is a wasteful number, since it uses less digits than its factorization.

640938240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 150 (or 133 counting only the distinct ones).

The product of its (nonzero) digits is 41472, while the sum is 36.

The square root of 640938240 is about 25316.7580862953. The cubic root of 640938240 is about 862.1947905602.

The spelling of 640938240 in words is "six hundred forty million, nine hundred thirty-eight thousand, two hundred forty".