21305000 has 40 divisors (see below), whose sum is σ = 49929330. Its totient is φ = 8520000.

The previous prime is 21304991. The next prime is 21305003. The reversal of 21305000 is 50312.

It can be written as a sum of positive squares in 5 ways, for example, as 3378244 + 17926756 = 1838^2 + 4234^2 .

It is a tau number, because it is divible by the number of its divisors (40).

It is not an unprimeable number, because it can be changed into a prime (21305003) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 2870 + ... + 7130.

Almost surely, 2^21305000 is an apocalyptic number.

21305000 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 21305000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24964665).

21305000 is an abundant number, since it is smaller than the sum of its proper divisors (28624330).

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

21305000 is an equidigital number, since it uses as much as digits as its factorization.

21305000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4287 (or 4268 counting only the distinct ones).

The product of its (nonzero) digits is 30, while the sum is 11.

The square root of 21305000 is about 4615.7339611377. The cubic root of 21305000 is about 277.2216726175.

Adding to 21305000 its reverse (50312), we get a palindrome (21355312).

The spelling of 21305000 in words is "twenty-one million, three hundred five thousand".