643845726541 has 2 divisors, whose sum is σ = 643845726542. Its totient is φ = 643845726540.

The previous prime is 643845726481. The next prime is 643845726569. The reversal of 643845726541 is 145627548346.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 533113181316 + 110732545225 = 730146^2 + 332765^2 .

It is a cyclic number.

It is not a de Polignac number, because 643845726541 - 2²¹ = 643843629389 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (643845726571) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321922863270 + 321922863271.

It is an arithmetic number, because the mean of its divisors is an integer number (321922863271).

Almost surely, 2^643845726541 is an apocalyptic number.

It is an amenable number.

643845726541 is a deficient number, since it is larger than the sum of its proper divisors (1).

643845726541 is an equidigital number, since it uses as much as digits as its factorization.

643845726541 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 19353600, while the sum is 55.

The spelling of 643845726541 in words is "six hundred forty-three billion, eight hundred forty-five million, seven hundred twenty-six thousand, five hundred forty-one".