21212100 has 324 divisors, whose sum is σ = 85544004.
Its totient is φ = 4354560.
The previous prime is 21212099. The next prime is 21212101. The reversal of 21212100 is 121212.
Adding to 21212100 its reverse (121212), we get a palindrome (21333312).
It can be divided in two parts, 21212 and 100, that added together give a palindrome (21312).
It is an interprime number because it is at equal distance from previous prime (21212099) and next prime (21212101).
It can be written as a sum of positive squares in 6 ways, for example, as 254016 + 20958084 = 504^2 + 4578^2
It is a super-3 number, since 3×212121003 (a number of 23 digits) contains 333 as substring.
It is a Harshad number since it is a multiple of its sum of digits (9).
It is not an unprimeable number, because it can be changed into a prime (21212101) by changing a digit.
It is a polite number, since it can be written in 107 ways as a sum of consecutive naturals, for example, 573282 + ... + 573318.
Almost surely, 221212100 is an apocalyptic number.
21212100 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 21212100, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (42772002).
21212100 is an abundant number, since it is smaller than the sum of its proper divisors (64331904).
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
21212100 is a wasteful number, since it uses less digits than its factorization.
21212100 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 84 (or 67 counting only the distinct ones).
The product of its (nonzero) digits is 8, while the sum is 9.
The square root of 21212100 is about 4605.6595618869.
The cubic root of 21212100 is about 276.8181457860.
The spelling of 21212100 in words is "twenty-one million, two hundred twelve thousand, one hundred".