643473521 has 2 divisors, whose sum is σ = 643473522. Its totient is φ = 643473520.

The previous prime is 643473517. The next prime is 643473527. The reversal of 643473521 is 125374346.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 386672896 + 256800625 = 19664^2 + 16025^2 .

It is a cyclic number.

It is not a de Polignac number, because 643473521 - 2² = 643473517 is a prime.

It is equal to p_33471692 and since 643473521 and 33471692 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (643473527) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321736760 + 321736761.

It is an arithmetic number, because the mean of its divisors is an integer number (321736761).

Almost surely, 2^643473521 is an apocalyptic number.

It is an amenable number.

643473521 is a deficient number, since it is larger than the sum of its proper divisors (1).

643473521 is an equidigital number, since it uses as much as digits as its factorization.

643473521 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 60480, while the sum is 35.

The square root of 643473521 is about 25366.7798705315. The cubic root of 643473521 is about 863.3301210689.

The spelling of 643473521 in words is "six hundred forty-three million, four hundred seventy-three thousand, five hundred twenty-one".