21438845 has 4 divisors (see below), whose sum is σ = 25726620. Its totient is φ = 17151072.

The previous prime is 21438839. The next prime is 21438847. The reversal of 21438845 is 54883412.

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 9174841 + 12264004 = 3029^2 + 3502^2 .

It is a cyclic number.

It is not a de Polignac number, because 21438845 - 2⁸ = 21438589 is a prime.

It is a Curzon number.

It is a plaindrome in base 11.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21438847) 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, 2143880 + ... + 2143889.

It is an arithmetic number, because the mean of its divisors is an integer number (6431655).

Almost surely, 2^21438845 is an apocalyptic number.

It is an amenable number.

21438845 is a deficient number, since it is larger than the sum of its proper divisors (4287775).

21438845 is an equidigital number, since it uses as much as digits as its factorization.

21438845 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4287774.

The product of its digits is 30720, while the sum is 35.

The square root of 21438845 is about 4630.2100384324. The cubic root of 21438845 is about 277.8009936448.

The spelling of 21438845 in words is "twenty-one million, four hundred thirty-eight thousand, eight hundred forty-five".