21000000000020 has 48 divisors (see below), whose sum is σ = 44596678064400. Its totient is φ = 8305399618560.

The previous prime is 21000000000013. The next prime is 21000000000149. The reversal of 21000000000020 is 2000000000012.

It can be written as a sum of positive squares in 8 ways, for example, as 1864169699716 + 19135830300304 = 1365346^2 + 4374452^2 .

It is a Harshad number since it is a multiple of its sum of digits (5).

It is a junction number, because it is equal to n+sod(n) for n = 20999999999923 and 21000000000013.

It is a congruent number.

It is an unprimeable number.

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 in 15 ways as a sum of consecutive naturals, for example, 78879530 + ... + 79145310.

It is an arithmetic number, because the mean of its divisors is an integer number (929097459675).

Almost surely, 2^{21000000000020} is an apocalyptic number.

21000000000020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21000000000020 is an abundant number, since it is smaller than the sum of its proper divisors (23596678064380).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21000000000020 is a wasteful number, since it uses less digits than its factorization.

21000000000020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 310268 (or 310266 counting only the distinct ones).

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

Adding to 21000000000020 its reverse (2000000000012), we get a palindrome (23000000000032).

The spelling of 21000000000020 in words is "twenty-one trillion, twenty", and thus it is an aban number and an uban number.