21321212220 has 216 divisors, whose sum is σ = 82073195568. Its totient is φ = 4430361600.

The previous prime is 21321212207. The next prime is 21321212233. The reversal of 21321212220 is 2221212312.

21321212220 is a `hidden beast` number, since 213 + 21 + 212 + 220 = 666.

It is an interprime number because it is at equal distance from previous prime (21321212207) and next prime (21321212233).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to n+sod(n) for n = 21321212193 and 21321212202.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 12861 + ... + 206900.

It is an arithmetic number, because the mean of its divisors is an integer number (379968498).

Almost surely, 2^21321212220 is an apocalyptic number.

21321212220 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 21321212220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (41036597784).

21321212220 is an abundant number, since it is smaller than the sum of its proper divisors (60751983348).

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

21321212220 is a wasteful number, since it uses less digits than its factorization.

21321212220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 219801 (or 219789 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 18.

Adding to 21321212220 its reverse (2221212312), we get a palindrome (23542424532).

The spelling of 21321212220 in words is "twenty-one billion, three hundred twenty-one million, two hundred twelve thousand, two hundred twenty".