21545253 has 6 divisors (see below), whose sum is σ = 31120934. Its totient is φ = 14363496.

The previous prime is 21545243. The next prime is 21545263. The reversal of 21545253 is 35254512.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21545243) and next prime (21545263).

It can be written as a sum of positive squares in only one way, i.e., 18507204 + 3038049 = 4302^2 + 1743^2 .

It is not a de Polignac number, because 21545253 - 2⁹ = 21544741 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21545203) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1196950 + ... + 1196967.

Almost surely, 2^21545253 is an apocalyptic number.

It is an amenable number.

21545253 is a deficient number, since it is larger than the sum of its proper divisors (9575681).

21545253 is a wasteful number, since it uses less digits than its factorization.

21545253 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2393923 (or 2393920 counting only the distinct ones).

The product of its digits is 6000, while the sum is 27.

The square root of 21545253 is about 4641.6864392158. The cubic root of 21545253 is about 278.2598410752.

Adding to 21545253 its reverse (35254512), we get a palindrome (56799765).

The spelling of 21545253 in words is "twenty-one million, five hundred forty-five thousand, two hundred fifty-three".