21812100 has 36 divisors (see below), whose sum is σ = 63110544. Its totient is φ = 5816480.

The previous prime is 21812083. The next prime is 21812107. The reversal of 21812100 is 121812.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a self number, because there is not a number n which added to its sum of digits gives 21812100.

It is not an unprimeable number, because it can be changed into a prime (21812107) 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 11 ways as a sum of consecutive naturals, for example, 36054 + ... + 36653.

Almost surely, 2^21812100 is an apocalyptic number.

21812100 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21812100 is an abundant number, since it is smaller than the sum of its proper divisors (41298444).

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

21812100 is a wasteful number, since it uses less digits than its factorization.

21812100 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 72724 (or 72717 counting only the distinct ones).

The product of its (nonzero) digits is 32, while the sum is 15.

The square root of 21812100 is about 4670.3425998528. The cubic root of 21812100 is about 279.4039190019.

Adding to 21812100 its reverse (121812), we get a palindrome (21933912).

It can be divided in two parts, 21812 and 100, that added together give a palindrome (21912).

The spelling of 21812100 in words is "twenty-one million, eight hundred twelve thousand, one hundred".