643664234223541 has 16 divisors (see below), whose sum is σ = 656214211559088. Its totient is φ = 631129314816000.

The previous prime is 643664234223523. The next prime is 643664234223557. The reversal of 643664234223541 is 145322432466346.

It can be written as a sum of positive squares in 8 ways, for example, as 49807544042916 + 593856690180625 = 7057446^2 + 24369175^2 .

It is a cyclic number.

It is not a de Polignac number, because 643664234223541 - 2³⁷ = 643526795270069 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643664234223341) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1580593545 + ... + 1581000721.

It is an arithmetic number, because the mean of its divisors is an integer number (41013388222443).

Almost surely, 2^{643664234223541} is an apocalyptic number.

It is an amenable number.

643664234223541 is a deficient number, since it is larger than the sum of its proper divisors (12549977335547).

643664234223541 is a wasteful number, since it uses less digits than its factorization.

643664234223541 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 425592.

The product of its digits is 59719680, while the sum is 55.

Adding to 643664234223541 its reverse (145322432466346), we get a palindrome (788986666689887).

The spelling of 643664234223541 in words is "six hundred forty-three trillion, six hundred sixty-four billion, two hundred thirty-four million, two hundred twenty-three thousand, five hundred forty-one".