21203253 has 6 divisors (see below), whose sum is σ = 30626934. Its totient is φ = 14135496.

The previous prime is 21203249. The next prime is 21203279. The reversal of 21203253 is 35230212.

It can be written as a sum of positive squares in only one way, i.e., 17114769 + 4088484 = 4137^2 + 2022^2 .

It is not a de Polignac number, because 21203253 - 2² = 21203249 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21203213) 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, 1177950 + ... + 1177967.

It is an arithmetic number, because the mean of its divisors is an integer number (5104489).

Almost surely, 2^21203253 is an apocalyptic number.

It is an amenable number.

21203253 is a deficient number, since it is larger than the sum of its proper divisors (9423681).

21203253 is a wasteful number, since it uses less digits than its factorization.

21203253 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2355923 (or 2355920 counting only the distinct ones).

The product of its (nonzero) digits is 360, while the sum is 18.

The square root of 21203253 is about 4604.6990129649. The cubic root of 21203253 is about 276.7796559510.

Adding to 21203253 its reverse (35230212), we get a palindrome (56433465).

The spelling of 21203253 in words is "twenty-one million, two hundred three thousand, two hundred fifty-three".