640161978624 has 540 divisors, whose sum is σ = 2235195843804. Its totient is φ = 181693145088.

The previous prime is 640161978607. The next prime is 640161978649. The reversal of 640161978624 is 426879161046.

640161978624 is a `hidden beast` number, since 6 + 4 + 0 + 1 + 6 + 1 + 9 + 7 + 8 + 624 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 370676404224 + 269485574400 = 608832^2 + 519120^2 .

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 59 ways as a sum of consecutive naturals, for example, 159520042 + ... + 159524054.

Almost surely, 2^640161978624 is an apocalyptic number.

640161978624 is a gapful number since it is divisible by the number (64) 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 640161978624, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1117597921902).

640161978624 is an abundant number, since it is smaller than the sum of its proper divisors (1595033865180).

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

640161978624 is a wasteful number, since it uses less digits than its factorization.

640161978624 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4212 (or 4182 counting only the distinct ones).

The product of its (nonzero) digits is 3483648, while the sum is 54.

The spelling of 640161978624 in words is "six hundred forty billion, one hundred sixty-one million, nine hundred seventy-eight thousand, six hundred twenty-four".