21250205 has 4 divisors (see below), whose sum is σ = 25500252. Its totient is φ = 17000160.

The previous prime is 21250199. The next prime is 21250211. The reversal of 21250205 is 50205212.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (21250199) and next prime (21250211).

It can be written as a sum of positive squares in 2 ways, for example, as 6832996 + 14417209 = 2614^2 + 3797^2 .

It is not a de Polignac number, because 21250205 - 2¹⁸ = 20988061 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2125016 + ... + 2125025.

It is an arithmetic number, because the mean of its divisors is an integer number (6375063).

Almost surely, 2^21250205 is an apocalyptic number.

It is an amenable number.

21250205 is a deficient number, since it is larger than the sum of its proper divisors (4250047).

21250205 is an equidigital number, since it uses as much as digits as its factorization.

21250205 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4250046.

The product of its (nonzero) digits is 200, while the sum is 17.

The square root of 21250205 is about 4609.7944639647. The cubic root of 21250205 is about 276.9838035250.

Adding to 21250205 its reverse (50205212), we get a palindrome (71455417).

The spelling of 21250205 in words is "twenty-one million, two hundred fifty thousand, two hundred five".