640028440 has 16 divisors (see below), whose sum is σ = 1440064080. Its totient is φ = 256011360.

The previous prime is 640028437. The next prime is 640028447. The reversal of 640028440 is 44820046.

It is a junction number, because it is equal to n+sod(n) for n = 640028399 and 640028408.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640028447) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8000316 + ... + 8000395.

It is an arithmetic number, because the mean of its divisors is an integer number (90004005).

Almost surely, 2^640028440 is an apocalyptic number.

It is an amenable number.

640028440 is an abundant number, since it is smaller than the sum of its proper divisors (800035640).

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

640028440 is a wasteful number, since it uses less digits than its factorization.

640028440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16000722 (or 16000718 counting only the distinct ones).

The product of its (nonzero) digits is 6144, while the sum is 28.

The square root of 640028440 is about 25298.7833699567. The cubic root of 640028440 is about 861.7866408492.

Adding to 640028440 its reverse (44820046), we get a palindrome (684848486).

The spelling of 640028440 in words is "six hundred forty million, twenty-eight thousand, four hundred forty".