21212121020 has 48 divisors (see below), whose sum is σ = 46051487328. Its totient is φ = 8202055680.

The previous prime is 21212120987. The next prime is 21212121023. The reversal of 21212121020 is 2012121212.

It is a junction number, because it is equal to n+sod(n) for n = 21212120986 and 21212121004.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21212121023) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 43721 + ... + 210560.

It is an arithmetic number, because the mean of its divisors is an integer number (959405986).

Almost surely, 2^21212121020 is an apocalyptic number.

21212121020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21212121020 is an abundant number, since it is smaller than the sum of its proper divisors (24839366308).

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

21212121020 is a wasteful number, since it uses less digits than its factorization.

21212121020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 254430 (or 254428 counting only the distinct ones).

The product of its (nonzero) digits is 32, while the sum is 14.

Adding to 21212121020 its reverse (2012121212), we get a palindrome (23224242232).

The spelling of 21212121020 in words is "twenty-one billion, two hundred twelve million, one hundred twenty-one thousand, twenty".