643977779346 has 192 divisors, whose sum is σ = 1643480616960. Its totient is φ = 180127584000.

The previous prime is 643977779323. The next prime is 643977779353.

643977779346 is a `hidden beast` number, since 64 + 3 + 97 + 77 + 79 + 346 = 666.

643977779346 is nontrivially palindromic in base 10.

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 140512171 + ... + 140516753.

It is an arithmetic number, because the mean of its divisors is an integer number (8559794880).

Almost surely, 2^643977779346 is an apocalyptic number.

643977779346 is a gapful number since it is divisible by the number (66) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 643977779346, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (821740308480).

643977779346 is an abundant number, since it is smaller than the sum of its proper divisors (999502837614).

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

643977779346 is a wasteful number, since it uses less digits than its factorization.

643977779346 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5573 (or 5570 counting only the distinct ones).

The product of its digits is 1008189504, while the sum is 72.

The spelling of 643977779346 in words is "six hundred forty-three billion, nine hundred seventy-seven million, seven hundred seventy-nine thousand, three hundred forty-six".