53

is the integer between.

Math features

 * 53 is an odd number.
 * 53 is a prime number. Therefore, 53 is a deficient number.
 * 53 is the first number of the form $$5 \cdot 10^n + 3$$ to be a prime number. The next two terms, 503 and 5003 is prime, though 50003 is a multiple of 31.
 * 53 in decimal is its palindrome in hexadecimal.