21730201 has 4 divisors (see below), whose sum is σ = 21739572. Its totient is φ = 21720832.

The previous prime is 21730169. The next prime is 21730249. The reversal of 21730201 is 10203712.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 16801801 + 4928400 = 4099^2 + 2220^2 .

It is a cyclic number.

It is not a de Polignac number, because 21730201 - 2⁵ = 21730169 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21730001) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1641 + ... + 6793.

It is an arithmetic number, because the mean of its divisors is an integer number (5434893).

Almost surely, 2^21730201 is an apocalyptic number.

It is an amenable number.

21730201 is a deficient number, since it is larger than the sum of its proper divisors (9371).

21730201 is an equidigital number, since it uses as much as digits as its factorization.

21730201 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9370.

The product of its (nonzero) digits is 84, while the sum is 16.

The square root of 21730201 is about 4661.5663676494. The cubic root of 21730201 is about 279.0537830480.

Adding to 21730201 its reverse (10203712), we get a palindrome (31933913).

The spelling of 21730201 in words is "twenty-one million, seven hundred thirty thousand, two hundred one".