21121002020 has 12 divisors (see below), whose sum is σ = 44354104284. Its totient is φ = 8448400800.

The previous prime is 21121001969. The next prime is 21121002029. The reversal of 21121002020 is 2020012112.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 9241745956 + 11879256064 = 96134^2 + 108992^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21121001992 and 21121002010.

It is not an unprimeable number, because it can be changed into a prime (21121002029) 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 in 3 ways as a sum of consecutive naturals, for example, 528025031 + ... + 528025070.

It is an arithmetic number, because the mean of its divisors is an integer number (3696175357).

Almost surely, 2^21121002020 is an apocalyptic number.

21121002020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21121002020 is an abundant number, since it is smaller than the sum of its proper divisors (23233102264).

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

21121002020 is a wasteful number, since it uses less digits than its factorization.

21121002020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1056050110 (or 1056050108 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 11.

Adding to 21121002020 its reverse (2020012112), we get a palindrome (23141014132).

The spelling of 21121002020 in words is "twenty-one billion, one hundred twenty-one million, two thousand, twenty".