641502081821 has 2 divisors, whose sum is σ = 641502081822. Its totient is φ = 641502081820.

The previous prime is 641502081793. The next prime is 641502081841. The reversal of 641502081821 is 128180205146.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 640264027225 + 1238054596 = 800165^2 + 35186^2 .

It is a cyclic number.

It is not a de Polignac number, because 641502081821 - 2¹⁰ = 641502080797 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (641502081841) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320751040910 + 320751040911.

It is an arithmetic number, because the mean of its divisors is an integer number (320751040911).

Almost surely, 2^641502081821 is an apocalyptic number.

It is an amenable number.

641502081821 is a deficient number, since it is larger than the sum of its proper divisors (1).

641502081821 is an equidigital number, since it uses as much as digits as its factorization.

641502081821 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 30720, while the sum is 38.

Adding to 641502081821 its reverse (128180205146), we get a palindrome (769682286967).

The spelling of 641502081821 in words is "six hundred forty-one billion, five hundred two million, eighty-one thousand, eight hundred twenty-one".