21121211020 has 96 divisors (see below), whose sum is σ = 54914025600. Its totient is φ = 6684417792.

The previous prime is 21121211011. The next prime is 21121211047. The reversal of 21121211020 is 2011212112.

It is a super-2 number, since 2×21121211020² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (13).

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 31 ways as a sum of consecutive naturals, for example, 273246 + ... + 341914.

It is an arithmetic number, because the mean of its divisors is an integer number (572021100).

Almost surely, 2^21121211020 is an apocalyptic number.

21121211020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21121211020, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27457012800).

21121211020 is an abundant number, since it is smaller than the sum of its proper divisors (33792814580).

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

21121211020 is a wasteful number, since it uses less digits than its factorization.

21121211020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 68724 (or 68696 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 13.

Adding to 21121211020 its reverse (2011212112), we get a palindrome (23132423132).

The spelling of 21121211020 in words is "twenty-one billion, one hundred twenty-one million, two hundred eleven thousand, twenty".