643891921920 has 352 divisors, whose sum is σ = 2464303712640. Its totient is φ = 158496030720.

The previous prime is 643891921879. The next prime is 643891921961. The reversal of 643891921920 is 29129198346.

643891921920 is a `hidden beast` number, since 6 + 438 + 9 + 19 + 2 + 192 + 0 = 666.

It is an interprime number because it is at equal distance from previous prime (643891921879) and next prime (643891921961).

It is a super-2 number, since 2×643891921920² (a number of 24 digits) contains 22 as substring.

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

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1617975 + ... + 1976265.

It is an arithmetic number, because the mean of its divisors is an integer number (7000862820).

Almost surely, 2^643891921920 is an apocalyptic number.

643891921920 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 643891921920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1232151856320).

643891921920 is an abundant number, since it is smaller than the sum of its proper divisors (1820411790720).

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

643891921920 is a wasteful number, since it uses less digits than its factorization.

643891921920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 358338 (or 358314 counting only the distinct ones).

The product of its (nonzero) digits is 1679616, while the sum is 54.

The spelling of 643891921920 in words is "six hundred forty-three billion, eight hundred ninety-one million, nine hundred twenty-one thousand, nine hundred twenty".