21320245 has 4 divisors (see below), whose sum is σ = 25584300. Its totient is φ = 17056192.

The previous prime is 21320239. The next prime is 21320267. The reversal of 21320245 is 54202312.

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

It can be written as a sum of positive squares in 2 ways, for example, as 15816529 + 5503716 = 3977^2 + 2346^2 .

It is a cyclic number.

It is not a de Polignac number, because 21320245 - 2⁵ = 21320213 is a prime.

It is a congruent number.

It is an unprimeable number.

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 3 ways as a sum of consecutive naturals, for example, 2132020 + ... + 2132029.

It is an arithmetic number, because the mean of its divisors is an integer number (6396075).

Almost surely, 2^21320245 is an apocalyptic number.

It is an amenable number.

21320245 is a deficient number, since it is larger than the sum of its proper divisors (4264055).

21320245 is an equidigital number, since it uses as much as digits as its factorization.

21320245 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4264054.

The product of its (nonzero) digits is 480, while the sum is 19.

The square root of 21320245 is about 4617.3850824899. The cubic root of 21320245 is about 277.2877797403.

Adding to 21320245 its reverse (54202312), we get a palindrome (75522557).

The spelling of 21320245 in words is "twenty-one million, three hundred twenty thousand, two hundred forty-five".