640778040 has 320 divisors, whose sum is σ = 2592691200. Its totient is φ = 138661632.

The previous prime is 640777993. The next prime is 640778051. The reversal of 640778040 is 40877046.

It is a happy number.

640778040 is a `hidden beast` number, since 640 + 7 + 7 + 8 + 0 + 4 + 0 = 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 = 640777986 and 640778004.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 430177 + ... + 431663.

It is an arithmetic number, because the mean of its divisors is an integer number (8102160).

Almost surely, 2^640778040 is an apocalyptic number.

640778040 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 640778040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1296345600).

640778040 is an abundant number, since it is smaller than the sum of its proper divisors (1951913160).

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

640778040 is a wasteful number, since it uses less digits than its factorization.

640778040 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1536 (or 1523 counting only the distinct ones).

The product of its (nonzero) digits is 37632, while the sum is 36.

The square root of 640778040 is about 25313.5939763598. The cubic root of 640778040 is about 862.1229505054.

The spelling of 640778040 in words is "six hundred forty million, seven hundred seventy-eight thousand, forty".