21011012020 has 24 divisors (see below), whose sum is σ = 44846457768. Its totient is φ = 8266627200.

The previous prime is 21011011997. The next prime is 21011012027. The reversal of 21011012020 is 2021011012.

It can be written as a sum of positive squares in 4 ways, for example, as 199487376 + 20811524644 = 14124^2 + 144262^2 .

It is a super-2 number, since 2×21011012020² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (10).

It is a junction number, because it is equal to n+sod(n) for n = 21011011988 and 21011012006.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21011012027) 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 7 ways as a sum of consecutive naturals, for example, 8609851 + ... + 8612290.

It is an arithmetic number, because the mean of its divisors is an integer number (1868602407).

Almost surely, 2^21011012020 is an apocalyptic number.

21011012020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21011012020 is an abundant number, since it is smaller than the sum of its proper divisors (23835445748).

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

21011012020 is a wasteful number, since it uses less digits than its factorization.

21011012020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17222211 (or 17222209 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 10.

Adding to 21011012020 its reverse (2021011012), we get a palindrome (23032023032).

The spelling of 21011012020 in words is "twenty-one billion, eleven million, twelve thousand, twenty".