643501541 has 2 divisors, whose sum is σ = 643501542. Its totient is φ = 643501540.

The previous prime is 643501513. The next prime is 643501577. The reversal of 643501541 is 145105346.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 365612641 + 277888900 = 19121^2 + 16670^2 .

It is a cyclic number.

It is not a de Polignac number, because 643501541 - 2⁶ = 643501477 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (643501841) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321750770 + 321750771.

It is an arithmetic number, because the mean of its divisors is an integer number (321750771).

Almost surely, 2^643501541 is an apocalyptic number.

It is an amenable number.

643501541 is a deficient number, since it is larger than the sum of its proper divisors (1).

643501541 is an equidigital number, since it uses as much as digits as its factorization.

643501541 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 7200, while the sum is 29.

The square root of 643501541 is about 25367.3321616602. The cubic root of 643501541 is about 863.3426520993.

Adding to 643501541 its reverse (145105346), we get a palindrome (788606887).

The spelling of 643501541 in words is "six hundred forty-three million, five hundred one thousand, five hundred forty-one".