21100212 has 144 divisors (see below), whose sum is σ = 65508352. Its totient is φ = 5598720.

The previous prime is 21100207. The next prime is 21100217. The reversal of 21100212 is 21200112.

It is an interprime number because it is at equal distance from previous prime (21100207) and next prime (21100217).

It is a Harshad number since it is a multiple of its sum of digits (9).

It is a junction number, because it is equal to n+sod(n) for n = 21100194 and 21100203.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21100217) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 289008 + ... + 289080.

Almost surely, 2^21100212 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21100212, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32754176).

21100212 is an abundant number, since it is smaller than the sum of its proper divisors (44408140).

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

21100212 is a wasteful number, since it uses less digits than its factorization.

21100212 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 158 (or 153 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 9.

The square root of 21100212 is about 4593.4967073026. The cubic root of 21100212 is about 276.3305742866.

Adding to 21100212 its reverse (21200112), we get a palindrome (42300324).

It can be divided in two parts, 21100 and 212, that added together give a palindrome (21312).

The spelling of 21100212 in words is "twenty-one million, one hundred thousand, two hundred twelve".