21012021020 has 48 divisors (see below), whose sum is σ = 45334967328. Its totient is φ = 8174557440.

The previous prime is 21012021001. The next prime is 21012021049. The reversal of 21012021020 is 2012021012.

It is a happy number.

It is a junction number, because it is equal to n+sod(n) for n = 21012020992 and 21012021010.

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, 3468314 + ... + 3474366.

It is an arithmetic number, because the mean of its divisors is an integer number (944478486).

Almost surely, 2^21012021020 is an apocalyptic number.

21012021020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21012021020 is an abundant number, since it is smaller than the sum of its proper divisors (24322946308).

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

21012021020 is a wasteful number, since it uses less digits than its factorization.

21012021020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10790 (or 10788 counting only the distinct ones).

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

Adding to 21012021020 its reverse (2012021012), we get a palindrome (23024042032).

The spelling of 21012021020 in words is "twenty-one billion, twelve million, twenty-one thousand, twenty".