21000104009 has 2 divisors, whose sum is σ = 21000104010. Its totient is φ = 21000104008.

The previous prime is 21000103991. The next prime is 21000104093. The reversal of 21000104009 is 90040100012.

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., 18131430409 + 2868673600 = 134653^2 + 53560^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21000104009 is a prime.

It is not a weakly prime, because it can be changed into another prime (21000104809) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10500052004 + 10500052005.

It is an arithmetic number, because the mean of its divisors is an integer number (10500052005).

Almost surely, 2^21000104009 is an apocalyptic number.

It is an amenable number.

21000104009 is a deficient number, since it is larger than the sum of its proper divisors (1).

21000104009 is an equidigital number, since it uses as much as digits as its factorization.

21000104009 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 72, while the sum is 17.

The spelling of 21000104009 in words is "twenty-one billion, one hundred four thousand, nine".