21024900 has 144 divisors (see below), whose sum is σ = 72912000. Its totient is φ = 5166720.

The previous prime is 21024889. The next prime is 21024907. The reversal of 21024900 is 942012.

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

It is not an unprimeable number, because it can be changed into a prime (21024907) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 34801 + ... + 35399.

Almost surely, 2^21024900 is an apocalyptic number.

21024900 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 21024900, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36456000).

21024900 is an abundant number, since it is smaller than the sum of its proper divisors (51887100).

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

21024900 is a wasteful number, since it uses less digits than its factorization.

21024900 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 635 (or 622 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 18.

The square root of 21024900 is about 4585.2917028255. The cubic root of 21024900 is about 276.0014177621.

Adding to 21024900 its reverse (942012), we get a palindrome (21966912).

The spelling of 21024900 in words is "twenty-one million, twenty-four thousand, nine hundred".