21121100 has 144 divisors (see below), whose sum is σ = 61829376. Its totient is φ = 6048000.

The previous prime is 21121099. The next prime is 21121129. The reversal of 21121100 is 112112.

It is a super-2 number, since 2×21121100² = 892201730420000, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 99995 + ... + 100205.

Almost surely, 2^21121100 is an apocalyptic number.

21121100 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 21121100, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30914688).

21121100 is an abundant number, since it is smaller than the sum of its proper divisors (40708276).

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

21121100 is a wasteful number, since it uses less digits than its factorization.

21121100 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 256 (or 249 counting only the distinct ones).

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

The square root of 21121100 is about 4595.7697940606. The cubic root of 21121100 is about 276.4217280222.

Adding to 21121100 its reverse (112112), we get a palindrome (21233212).

It can be divided in two parts, 211 and 21100, that multiplied together give a square (4452100 = 2110²).

The spelling of 21121100 in words is "twenty-one million, one hundred twenty-one thousand, one hundred".