21005200 has 60 divisors (see below), whose sum is σ = 53450820. Its totient is φ = 7905280.

The previous prime is 21005191. The next prime is 21005209. The reversal of 21005200 is 250012.

It is an interprime number because it is at equal distance from previous prime (21005191) and next prime (21005209).

It can be written as a sum of positive squares in 6 ways, for example, as 1327104 + 19678096 = 1152^2 + 4436^2 .

It is a Harshad number since it is a multiple of its sum of digits (10).

It is not an unprimeable number, because it can be changed into a prime (21005209) 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 11 ways as a sum of consecutive naturals, for example, 5256 + ... + 8344.

It is an arithmetic number, because the mean of its divisors is an integer number (890847).

Almost surely, 2^21005200 is an apocalyptic number.

21005200 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 21005200, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26725410).

21005200 is an abundant number, since it is smaller than the sum of its proper divisors (32445620).

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

21005200 is a wasteful number, since it uses less digits than its factorization.

21005200 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3124 (or 3113 counting only the distinct ones).

The product of its (nonzero) digits is 20, while the sum is 10.

The square root of 21005200 is about 4583.1430263521. The cubic root of 21005200 is about 275.9151878313.

Adding to 21005200 its reverse (250012), we get a palindrome (21255212).

The spelling of 21005200 in words is "twenty-one million, five thousand, two hundred".