21653253 has 6 divisors (see below), whose sum is σ = 31276934. Its totient is φ = 14435496.

The previous prime is 21653243. The next prime is 21653267. The reversal of 21653253 is 35235612.

21653253 is a `hidden beast` number, since 2 + 1 + 653 + 2 + 5 + 3 = 666.

It can be written as a sum of positive squares in only one way, i.e., 14265729 + 7387524 = 3777^2 + 2718^2 .

It is not a de Polignac number, because 21653253 - 2⁴ = 21653237 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21653243) 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, 1202950 + ... + 1202967.

Almost surely, 2^21653253 is an apocalyptic number.

It is an amenable number.

21653253 is a deficient number, since it is larger than the sum of its proper divisors (9623681).

21653253 is a wasteful number, since it uses less digits than its factorization.

21653253 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2405923 (or 2405920 counting only the distinct ones).

The product of its digits is 5400, while the sum is 27.

The square root of 21653253 is about 4653.3055992488. The cubic root of 21653253 is about 278.7240111975.

Adding to 21653253 its reverse (35235612), we get a palindrome (56888865).

The spelling of 21653253 in words is "twenty-one million, six hundred fifty-three thousand, two hundred fifty-three".