21253243 has 4 divisors (see below), whose sum is σ = 23185368. Its totient is φ = 19321120.

The previous prime is 21253241. The next prime is 21253277. The reversal of 21253243 is 34235212.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21253243 - 2¹ = 21253241 is a prime.

It is a Smith number, since the sum of its digits (22) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21253241) 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, 966046 + ... + 966067.

It is an arithmetic number, because the mean of its divisors is an integer number (5796342).

Almost surely, 2^21253243 is an apocalyptic number.

21253243 is a deficient number, since it is larger than the sum of its proper divisors (1932125).

21253243 is a wasteful number, since it uses less digits than its factorization.

21253243 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1932124.

The product of its digits is 1440, while the sum is 22.

The square root of 21253243 is about 4610.1239679644. The cubic root of 21253243 is about 276.9970024047.

Adding to 21253243 its reverse (34235212), we get a palindrome (55488455).

The spelling of 21253243 in words is "twenty-one million, two hundred fifty-three thousand, two hundred forty-three".