21445205 has 18 divisors (see below), whose sum is σ = 27411426. Its totient is φ = 16104096.

The previous prime is 21445201. The next prime is 21445217. The reversal of 21445205 is 50254412.

It is a happy number.

It can be written as a sum of positive squares in 3 ways, for example, as 5373124 + 16072081 = 2318^2 + 4009^2 .

It is not a de Polignac number, because 21445205 - 2² = 21445201 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21445201) 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 17 ways as a sum of consecutive naturals, for example, 196691 + ... + 196799.

It is an arithmetic number, because the mean of its divisors is an integer number (1522857).

Almost surely, 2^21445205 is an apocalyptic number.

It is an amenable number.

21445205 is a deficient number, since it is larger than the sum of its proper divisors (5966221).

21445205 is an equidigital number, since it uses as much as digits as its factorization.

21445205 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 261 (or 133 counting only the distinct ones).

The product of its (nonzero) digits is 1600, while the sum is 23.

The square root of 21445205 is about 4630.8967814021. The cubic root of 21445205 is about 277.8284615368.

Adding to 21445205 its reverse (50254412), we get a palindrome (71699617).

The spelling of 21445205 in words is "twenty-one million, four hundred forty-five thousand, two hundred five".