20011000021 has 2 divisors, whose sum is σ = 20011000022. Its totient is φ = 20011000020.

The previous prime is 20011000019. The next prime is 20011000027. The reversal of 20011000021 is 12000011002.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19387499121 + 623500900 = 139239^2 + 24970^2 .

It is a cyclic number.

It is not a de Polignac number, because 20011000021 - 2¹ = 20011000019 is a prime.

Together with 20011000019, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 20010999968 and 20011000013.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20011000027) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10005500010 + 10005500011.

It is an arithmetic number, because the mean of its divisors is an integer number (10005500011).

Almost surely, 2^20011000021 is an apocalyptic number.

It is an amenable number.

20011000021 is a deficient number, since it is larger than the sum of its proper divisors (1).

20011000021 is an equidigital number, since it uses as much as digits as its factorization.

20011000021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4, while the sum is 7.

Adding to 20011000021 its reverse (12000011002), we get a palindrome (32011011023).

The spelling of 20011000021 in words is "twenty billion, eleven million, twenty-one", and thus it is an aban number and an uban number.