21725245 has 4 divisors (see below), whose sum is σ = 26070300. Its totient is φ = 17380192.

The previous prime is 21725239. The next prime is 21725273. The reversal of 21725245 is 54252712.

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 7901721 + 13823524 = 2811^2 + 3718^2 .

It is a cyclic number.

It is not a de Polignac number, because 21725245 - 2⁵ = 21725213 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, 2172520 + ... + 2172529.

It is an arithmetic number, because the mean of its divisors is an integer number (6517575).

Almost surely, 2^21725245 is an apocalyptic number.

It is an amenable number.

21725245 is a deficient number, since it is larger than the sum of its proper divisors (4345055).

21725245 is an equidigital number, since it uses as much as digits as its factorization.

21725245 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4345054.

The product of its digits is 5600, while the sum is 28.

The square root of 21725245 is about 4661.0347563604. The cubic root of 21725245 is about 279.0325668660.

Adding to 21725245 its reverse (54252712), we get a palindrome (75977957).

The spelling of 21725245 in words is "twenty-one million, seven hundred twenty-five thousand, two hundred forty-five".