21408100 has 108 divisors (see below), whose sum is σ = 57441636. Its totient is φ = 6881280.

The previous prime is 21408097. The next prime is 21408103. The reversal of 21408100 is 180412.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21408097) and next prime (21408103).

It can be written as a sum of positive squares in 6 ways, for example, as 2328676 + 19079424 = 1526^2 + 4368^2 .

It is a super-2 number, since 2×21408100² = 916613491220000, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21408103) 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 35 ways as a sum of consecutive naturals, for example, 83172 + ... + 83428.

It is an arithmetic number, because the mean of its divisors is an integer number (531867).

Almost surely, 2^21408100 is an apocalyptic number.

21408100 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 21408100, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28720818).

21408100 is an abundant number, since it is smaller than the sum of its proper divisors (36033536).

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

21408100 is a wasteful number, since it uses less digits than its factorization.

21408100 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 302 (or 288 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 16.

The square root of 21408100 is about 4626.8888035050. Note that the first 4 decimals coincide. The cubic root of 21408100 is about 277.6681339125.

Adding to 21408100 its reverse (180412), we get a palindrome (21588512).

The spelling of 21408100 in words is "twenty-one million, four hundred eight thousand, one hundred".