21121100220 has 384 divisors, whose sum is σ = 70183314432. Its totient is φ = 4689100800.

The previous prime is 21121100173. The next prime is 21121100227. The reversal of 21121100220 is 2200112112.

It is a super-2 number, since 2×21121100220² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (12).

It is a junction number, because it is equal to n+sod(n) for n = 21121100196 and 21121100205.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21121100227) by changing a digit.

It is a polite number, since it can be written in 127 ways as a sum of consecutive naturals, for example, 87639300 + ... + 87639540.

It is an arithmetic number, because the mean of its divisors is an integer number (182769048).

Almost surely, 2^21121100220 is an apocalyptic number.

21121100220 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 21121100220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35091657216).

21121100220 is an abundant number, since it is smaller than the sum of its proper divisors (49062214212).

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

21121100220 is a wasteful number, since it uses less digits than its factorization.

21121100220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 461 (or 459 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 12.

Adding to 21121100220 its reverse (2200112112), we get a palindrome (23321212332).

The spelling of 21121100220 in words is "twenty-one billion, one hundred twenty-one million, one hundred thousand, two hundred twenty".