643621541 has 2 divisors, whose sum is σ = 643621542. Its totient is φ = 643621540.

The previous prime is 643621519. The next prime is 643621577. The reversal of 643621541 is 145126346.

643621541 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 554790916 + 88830625 = 23554^2 + 9425^2 .

It is a cyclic number.

It is not a de Polignac number, because 643621541 - 2²² = 639427237 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 643621498 and 643621507.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (643671541) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321810770 + 321810771.

It is an arithmetic number, because the mean of its divisors is an integer number (321810771).

Almost surely, 2^643621541 is an apocalyptic number.

It is an amenable number.

643621541 is a deficient number, since it is larger than the sum of its proper divisors (1).

643621541 is an equidigital number, since it uses as much as digits as its factorization.

643621541 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 17280, while the sum is 32.

The square root of 643621541 is about 25369.6972981547. The cubic root of 643621541 is about 863.3963140682.

Adding to 643621541 its reverse (145126346), we get a palindrome (788747887).

The spelling of 643621541 in words is "six hundred forty-three million, six hundred twenty-one thousand, five hundred forty-one".