21324505 has 4 divisors (see below), whose sum is σ = 25589412. Its totient is φ = 17059600.

The previous prime is 21324503. The next prime is 21324509. The reversal of 21324505 is 50542312.

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 16842816 + 4481689 = 4104^2 + 2117^2 .

It is not a de Polignac number, because 21324505 - 2¹ = 21324503 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21324503) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2132446 + ... + 2132455.

It is an arithmetic number, because the mean of its divisors is an integer number (6397353).

Almost surely, 2^21324505 is an apocalyptic number.

It is an amenable number.

21324505 is a deficient number, since it is larger than the sum of its proper divisors (4264907).

21324505 is an equidigital number, since it uses as much as digits as its factorization.

21324505 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4264906.

The product of its (nonzero) digits is 1200, while the sum is 22.

The square root of 21324505 is about 4617.8463595057. The cubic root of 21324505 is about 277.3062468089.

Adding to 21324505 its reverse (50542312), we get a palindrome (71866817).

The spelling of 21324505 in words is "twenty-one million, three hundred twenty-four thousand, five hundred five".