21245400 has 288 divisors, whose sum is σ = 82695600. Its totient is φ = 4838400.

The previous prime is 21245387. The next prime is 21245407. The reversal of 21245400 is 454212.

21245400 is a `hidden beast` number, since 2 + 124 + 540 + 0 = 666.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21245407) 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 71 ways as a sum of consecutive naturals, for example, 574182 + ... + 574218.

Almost surely, 2^21245400 is an apocalyptic number.

21245400 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 21245400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (41347800).

21245400 is an abundant number, since it is smaller than the sum of its proper divisors (61450200).

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

21245400 is a wasteful number, since it uses less digits than its factorization.

21245400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 99 (or 87 counting only the distinct ones).

The product of its (nonzero) digits is 320, while the sum is 18.

The square root of 21245400 is about 4609.2732615891. The cubic root of 21245400 is about 276.9629251774.

Adding to 21245400 its reverse (454212), we get a palindrome (21699612).

The spelling of 21245400 in words is "twenty-one million, two hundred forty-five thousand, four hundred".