640927840 has 144 divisors (see below), whose sum is σ = 1822791600. Its totient is φ = 212093952.

The previous prime is 640927799. The next prime is 640927841. The reversal of 640927840 is 48729046.

It is a Harshad number since it is a multiple of its sum of digits (40).

It is a junction number, because it is equal to n+sod(n) for n = 640927793 and 640927802.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640927841) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 225951 + ... + 228769.

It is an arithmetic number, because the mean of its divisors is an integer number (12658275).

Almost surely, 2^640927840 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 640927840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (911395800).

640927840 is an abundant number, since it is smaller than the sum of its proper divisors (1181863760).

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

640927840 is a wasteful number, since it uses less digits than its factorization.

640927840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2877 (or 2862 counting only the distinct ones).

The product of its (nonzero) digits is 96768, while the sum is 40.

The square root of 640927840 is about 25316.5526879155. The cubic root of 640927840 is about 862.1901271497.

The spelling of 640927840 in words is "six hundred forty million, nine hundred twenty-seven thousand, eight hundred forty".