21207573 has 6 divisors (see below), whose sum is σ = 30633174. Its totient is φ = 14138376.

The previous prime is 21207569. The next prime is 21207581. The reversal of 21207573 is 37570212.

It can be written as a sum of positive squares in only one way, i.e., 12404484 + 8803089 = 3522^2 + 2967^2 .

It is not a de Polignac number, because 21207573 - 2² = 21207569 is a prime.

It is a super-2 number, since 2×21207573² = 899522305100658, which contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21207533) by changing a digit.

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 5 ways as a sum of consecutive naturals, for example, 1178190 + ... + 1178207.

It is an arithmetic number, because the mean of its divisors is an integer number (5105529).

Almost surely, 2^21207573 is an apocalyptic number.

It is an amenable number.

21207573 is a deficient number, since it is larger than the sum of its proper divisors (9425601).

21207573 is a wasteful number, since it uses less digits than its factorization.

21207573 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2356403 (or 2356400 counting only the distinct ones).

The product of its (nonzero) digits is 2940, while the sum is 27.

The square root of 21207573 is about 4605.1680751087. The cubic root of 21207573 is about 276.7984519178.

Adding to 21207573 its reverse (37570212), we get a palindrome (58777785).

The spelling of 21207573 in words is "twenty-one million, two hundred seven thousand, five hundred seventy-three".