20000000000021 has 2 divisors, whose sum is σ = 20000000000022. Its totient is φ = 20000000000020.

The previous prime is 19999999999997. The next prime is 20000000000041. The reversal of 20000000000021 is 12000000000002.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11744945868100 + 8255054131921 = 3427090^2 + 2873161^2 .

It is a cyclic number.

It is not a de Polignac number, because 20000000000021 - 2⁶ = 19999999999957 is a prime.

20000000000021 is a modest number, since divided by 21 gives 20 as remainder.

It is a junction number, because it is equal to n+sod(n) for n = 19999999999915 and 20000000000014.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20000000000041) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10000000000010 + 10000000000011.

It is an arithmetic number, because the mean of its divisors is an integer number (10000000000011).

Almost surely, 2^{20000000000021} is an apocalyptic number.

It is an amenable number.

20000000000021 is a deficient number, since it is larger than the sum of its proper divisors (1).

20000000000021 is an equidigital number, since it uses as much as digits as its factorization.

20000000000021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4, while the sum is 5.

Adding to 20000000000021 its reverse (12000000000002), we get a palindrome (32000000000023).

The spelling of 20000000000021 in words is "twenty trillion, twenty-one", and thus it is an aban number and an uban number.