641638009 has 2 divisors, whose sum is σ = 641638010. Its totient is φ = 641638008.

The previous prime is 641638003. The next prime is 641638013. The reversal of 641638009 is 900836146.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 416037609 + 225600400 = 20397^2 + 15020^2 .

It is a cyclic number.

It is not a de Polignac number, because 641638009 - 2³ = 641638001 is a prime.

It is not a weakly prime, because it can be changed into another prime (641638001) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320819004 + 320819005.

It is an arithmetic number, because the mean of its divisors is an integer number (320819005).

Almost surely, 2^641638009 is an apocalyptic number.

It is an amenable number.

641638009 is a deficient number, since it is larger than the sum of its proper divisors (1).

641638009 is an equidigital number, since it uses as much as digits as its factorization.

641638009 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 31104, while the sum is 37.

The square root of 641638009 is about 25330.5745888245. The cubic root of 641638009 is about 862.5084545555.

The spelling of 641638009 in words is "six hundred forty-one million, six hundred thirty-eight thousand, nine".