21121002028 has 144 divisors (see below), whose sum is σ = 47106630144. Its totient is φ = 8099942400.

The previous prime is 21121001969. The next prime is 21121002029. The reversal of 21121002028 is 82020012112.

It is a super-2 number, since 2×21121002028² (a number of 21 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21121001996 and 21121002014.

It is not an unprimeable number, because it can be changed into a prime (21121002029) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 52670628 + ... + 52671028.

It is an arithmetic number, because the mean of its divisors is an integer number (327129376).

Almost surely, 2^21121002028 is an apocalyptic number.

21121002028 is a gapful number since it is divisible by the number (28) 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 21121002028, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23553315072).

21121002028 is an abundant number, since it is smaller than the sum of its proper divisors (25985628116).

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

21121002028 is a wasteful number, since it uses less digits than its factorization.

21121002028 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 752 (or 733 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 19.

The spelling of 21121002028 in words is "twenty-one billion, one hundred twenty-one million, two thousand, twenty-eight".