21211100 has 36 divisors (see below), whose sum is σ = 47017824. Its totient is φ = 8302080.

The previous prime is 21211079. The next prime is 21211109. The reversal of 21211100 is 111212.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21211109) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2444 + ... + 6956.

Almost surely, 2^21211100 is an apocalyptic number.

21211100 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 21211100, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23508912).

21211100 is an abundant number, since it is smaller than the sum of its proper divisors (25806724).

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

21211100 is a wasteful number, since it uses less digits than its factorization.

21211100 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4574 (or 4567 counting only the distinct ones).

The product of its (nonzero) digits is 4, while the sum is 8.

The square root of 21211100 is about 4605.5509985234. The cubic root of 21211100 is about 276.8137957139.

Adding to 21211100 its reverse (111212), we get a palindrome (21322312).

The spelling of 21211100 in words is "twenty-one million, two hundred eleven thousand, one hundred".