643221644121 has 81 divisors (see below), whose sum is σ = 1091966661279. Its totient is φ = 363792189600.

The previous prime is 643221644119. The next prime is 643221644147. The reversal of 643221644121 is 121446122346.

643221644121 = 1³ + 2³ + ... + 1266³.

The square root of 643221644121 is 802011.

It is a perfect power (a square), and thus also a powerful number.

643221644121 is a `hidden beast` number, since 6 + 4 + 3 + 2 + 2 + 1 + 644 + 1 + 2 + 1 = 666.

It can be written as a sum of positive squares in only one way, i.e., 7087787721 + 636133856400 = 84189^2 + 797580^2 .

It is not a de Polignac number, because 643221644121 - 2¹ = 643221644119 is a prime.

It is not an unprimeable number, because it can be changed into a prime (643221644621) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 80 ways as a sum of consecutive naturals, for example, 3048443706 + ... + 3048443916.

Almost surely, 2^643221644121 is an apocalyptic number.

643221644121 is the 802011-st square number.

643221644121 is the 401006-th centered octagonal number.

It is an amenable number.

643221644121 is a deficient number, since it is larger than the sum of its proper divisors (448745017158).

643221644121 is an equidigital number, since it uses as much as digits as its factorization.

643221644121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 804 (or 402 counting only the distinct ones).

The product of its digits is 55296, while the sum is 36.

Multiplying 643221644121 by its sum of digits (36), we get a square (23155979188356 = 4812066²).

Adding to 643221644121 its reverse (121446122346), we get a palindrome (764667766467).

The spelling of 643221644121 in words is "six hundred forty-three billion, two hundred twenty-one million, six hundred forty-four thousand, one hundred twenty-one".