21211021020 has 72 divisors (see below), whose sum is σ = 69087335184. Its totient is φ = 4848232704.

The previous prime is 21211021003. The next prime is 21211021081. The reversal of 21211021020 is 2012011212.

It is a Harshad number since it is a multiple of its sum of digits (12).

It is a junction number, because it is equal to n+sod(n) for n = 21211020987 and 21211021005.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 3604377 + ... + 3610256.

It is an arithmetic number, because the mean of its divisors is an integer number (959546322).

Almost surely, 2^21211021020 is an apocalyptic number.

21211021020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21211021020 is an abundant number, since it is smaller than the sum of its proper divisors (47876314164).

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

21211021020 is a wasteful number, since it uses less digits than its factorization.

21211021020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7214659 (or 7214650 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 12.

Adding to 21211021020 its reverse (2012011212), we get a palindrome (23223032232).

The spelling of 21211021020 in words is "twenty-one billion, two hundred eleven million, twenty-one thousand, twenty".