21217573 has 4 divisors (see below), whose sum is σ = 22849708. Its totient is φ = 19585440.

The previous prime is 21217571. The next prime is 21217577. The reversal of 21217573 is 37571212.

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 11276164 + 9941409 = 3358^2 + 3153^2 .

It is a cyclic number.

It is not a de Polignac number, because 21217573 - 2¹ = 21217571 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 (21217571) 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, 816048 + ... + 816073.

It is an arithmetic number, because the mean of its divisors is an integer number (5712427).

Almost surely, 2^21217573 is an apocalyptic number.

It is an amenable number.

21217573 is a deficient number, since it is larger than the sum of its proper divisors (1632135).

21217573 is a wasteful number, since it uses less digits than its factorization.

21217573 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1632134.

The product of its digits is 2940, while the sum is 28.

The square root of 21217573 is about 4606.2536838520. The cubic root of 21217573 is about 276.8419513095.

Adding to 21217573 its reverse (37571212), we get a palindrome (58788785).

The spelling of 21217573 in words is "twenty-one million, two hundred seventeen thousand, five hundred seventy-three".