20002000021 has 2 divisors, whose sum is σ = 20002000022. Its totient is φ = 20002000020.

The previous prime is 20001999977. The next prime is 20002000033. The reversal of 20002000021 is 12000020002.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19941393796 + 60606225 = 141214^2 + 7785^2 .

It is a cyclic number.

It is not a de Polignac number, because 20002000021 - 2¹³ = 20001991829 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 20001999968 and 20002000013.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20002000121) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10001000010 + 10001000011.

It is an arithmetic number, because the mean of its divisors is an integer number (10001000011).

Almost surely, 2^20002000021 is an apocalyptic number.

It is an amenable number.

20002000021 is a deficient number, since it is larger than the sum of its proper divisors (1).

20002000021 is an equidigital number, since it uses as much as digits as its factorization.

20002000021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 8, while the sum is 7.

Adding to 20002000021 its reverse (12000020002), we get a palindrome (32002020023).

The spelling of 20002000021 in words is "twenty billion, two million, twenty-one", and thus it is an aban number and an uban number.