21221212020 has 24 divisors (see below), whose sum is σ = 59419393824. Its totient is φ = 5658989856.

The previous prime is 21221211989. The next prime is 21221212049. The reversal of 21221212020 is 2021212212.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 176843374 + ... + 176843493.

It is an arithmetic number, because the mean of its divisors is an integer number (2475808076).

Almost surely, 2^21221212020 is an apocalyptic number.

21221212020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21221212020 is an abundant number, since it is smaller than the sum of its proper divisors (38198181804).

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

21221212020 is a wasteful number, since it uses less digits than its factorization.

21221212020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 353686879 (or 353686877 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 15.

Adding to 21221212020 its reverse (2021212212), we get a palindrome (23242424232).

The spelling of 21221212020 in words is "twenty-one billion, two hundred twenty-one million, two hundred twelve thousand, twenty".