21100100 has 72 divisors (see below), whose sum is σ = 53621568. Its totient is φ = 7056000.

The previous prime is 21100097. The next prime is 21100103. The reversal of 21100100 is 100112.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21100097) and next prime (21100103).

It is a Harshad number since it is a multiple of its sum of digits (5).

It is not an unprimeable number, because it can be changed into a prime (21100103) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 29750 + ... + 30450.

It is an arithmetic number, because the mean of its divisors is an integer number (744744).

Almost surely, 2^21100100 is an apocalyptic number.

21100100 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 21100100, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26810784).

21100100 is an abundant number, since it is smaller than the sum of its proper divisors (32521468).

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

21100100 is a wasteful number, since it uses less digits than its factorization.

21100100 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 765 (or 758 counting only the distinct ones).

The product of its (nonzero) digits is 2, while the sum is 5.

The square root of 21100100 is about 4593.4845161380. The cubic root of 21100100 is about 276.3300853645.

Adding to 21100100 its reverse (100112), we get a palindrome (21200212).

The spelling of 21100100 in words is "twenty-one million, one hundred thousand, one hundred".