21208500 has 96 divisors (see below), whose sum is σ = 68664960. Its totient is φ = 5652000.

The previous prime is 21208493. The next prime is 21208513. The reversal of 21208500 is 580212.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 12715 + ... + 14285.

It is an arithmetic number, because the mean of its divisors is an integer number (715260).

Almost surely, 2^21208500 is an apocalyptic number.

21208500 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 21208500, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34332480).

21208500 is an abundant number, since it is smaller than the sum of its proper divisors (47456460).

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

21208500 is a wasteful number, since it uses less digits than its factorization.

21208500 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1599 (or 1581 counting only the distinct ones).

The product of its (nonzero) digits is 160, while the sum is 18.

The square root of 21208500 is about 4605.2687218012. The cubic root of 21208500 is about 276.8024848864.

Adding to 21208500 its reverse (580212), we get a palindrome (21788712).

The spelling of 21208500 in words is "twenty-one million, two hundred eight thousand, five hundred".