641605981 has 2 divisors, whose sum is σ = 641605982. Its totient is φ = 641605980.

The previous prime is 641605973. The next prime is 641606033. The reversal of 641605981 is 189506146.

641605981 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 366377881 + 275228100 = 19141^2 + 16590^2 .

It is a cyclic number.

It is not a de Polignac number, because 641605981 - 2³ = 641605973 is a prime.

It is a super-2 number, since 2×641605981² = 823316469709944722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (641605931) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320802990 + 320802991.

It is an arithmetic number, because the mean of its divisors is an integer number (320802991).

Almost surely, 2^641605981 is an apocalyptic number.

It is an amenable number.

641605981 is a deficient number, since it is larger than the sum of its proper divisors (1).

641605981 is an equidigital number, since it uses as much as digits as its factorization.

641605981 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 51840, while the sum is 40.

The square root of 641605981 is about 25329.9423805109. The cubic root of 641605981 is about 862.4941033273.

The spelling of 641605981 in words is "six hundred forty-one million, six hundred five thousand, nine hundred eighty-one".