21012012020 has 48 divisors (see below), whose sum is σ = 46124926848. Its totient is φ = 8025198720.

The previous prime is 21012011989. The next prime is 21012012067. The reversal of 21012012020 is 2021021012.

It is a happy number.

It is a junction number, because it is equal to n+sod(n) for n = 21012011992 and 21012012010.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 222662 + ... + 302658.

It is an arithmetic number, because the mean of its divisors is an integer number (960935976).

Almost surely, 2^21012012020 is an apocalyptic number.

21012012020 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 21012012020, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23062463424).

21012012020 is an abundant number, since it is smaller than the sum of its proper divisors (25112914828).

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

21012012020 is a wasteful number, since it uses less digits than its factorization.

21012012020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 80600 (or 80598 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 11.

Adding to 21012012020 its reverse (2021021012), we get a palindrome (23033033032).

The spelling of 21012012020 in words is "twenty-one billion, twelve million, twelve thousand, twenty".