643544641 has 2 divisors, whose sum is σ = 643544642. Its totient is φ = 643544640.

The previous prime is 643544609. The next prime is 643544647. The reversal of 643544641 is 146445346.

643544641 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 541958400 + 101586241 = 23280^2 + 10079^2 .

It is a cyclic number.

It is not a de Polignac number, because 643544641 - 2⁵ = 643544609 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 643544641.

It is not a weakly prime, because it can be changed into another prime (643544647) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321772320 + 321772321.

It is an arithmetic number, because the mean of its divisors is an integer number (321772321).

Almost surely, 2^643544641 is an apocalyptic number.

It is an amenable number.

643544641 is a deficient number, since it is larger than the sum of its proper divisors (1).

643544641 is an equidigital number, since it uses as much as digits as its factorization.

643544641 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 138240, while the sum is 37.

The square root of 643544641 is about 25368.1816652278. The cubic root of 643544641 is about 863.3619264575.

Adding to 643544641 its reverse (146445346), we get a palindrome (789989987).

It can be divided in two parts, 6435 and 44641, that added together give a square (51076 = 226²).

The spelling of 643544641 in words is "six hundred forty-three million, five hundred forty-four thousand, six hundred forty-one".