21010121020 has 72 divisors (see below), whose sum is σ = 51409388016. Its totient is φ = 7191588096.

The previous prime is 21010120951. The next prime is 21010121137. The reversal of 21010121020 is 2012101012.

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 = 21010120988 and 21010121006.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 587287 + ... + 622033.

It is an arithmetic number, because the mean of its divisors is an integer number (714019278).

Almost surely, 2^21010121020 is an apocalyptic number.

21010121020 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 21010121020, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25704694008).

21010121020 is an abundant number, since it is smaller than the sum of its proper divisors (30399266996).

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

21010121020 is a wasteful number, since it uses less digits than its factorization.

21010121020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 35387 (or 35378 counting only the distinct ones).

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

Adding to 21010121020 its reverse (2012101012), we get a palindrome (23022222032).

The spelling of 21010121020 in words is "twenty-one billion, ten million, one hundred twenty-one thousand, twenty".