21002000009 has 2 divisors, whose sum is σ = 21002000010. Its totient is φ = 21002000008.

The previous prime is 21001999973. The next prime is 21002000017. The reversal of 21002000009 is 90000020012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19886640400 + 1115359609 = 141020^2 + 33397^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21002000009 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21001999957 and 21002000002.

It is not a weakly prime, because it can be changed into another prime (21002000059) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10501000004 + 10501000005.

It is an arithmetic number, because the mean of its divisors is an integer number (10501000005).

Almost surely, 2^21002000009 is an apocalyptic number.

It is an amenable number.

21002000009 is a deficient number, since it is larger than the sum of its proper divisors (1).

21002000009 is an equidigital number, since it uses as much as digits as its factorization.

21002000009 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 36, while the sum is 14.

The spelling of 21002000009 in words is "twenty-one billion, two million, nine", and thus it is an aban number and an uban number.