21105253 has 8 divisors (see below), whose sum is σ = 22765400. Its totient is φ = 19450368.

The previous prime is 21105239. The next prime is 21105307. The reversal of 21105253 is 35250112.

It can be written as a sum of positive squares in 4 ways, for example, as 3448449 + 17656804 = 1857^2 + 4202^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21105253 - 2⁵ = 21105221 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21105253.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21105233) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 12313 + ... + 13921.

It is an arithmetic number, because the mean of its divisors is an integer number (2845675).

Almost surely, 2^21105253 is an apocalyptic number.

It is an amenable number.

21105253 is a deficient number, since it is larger than the sum of its proper divisors (1660147).

21105253 is a wasteful number, since it uses less digits than its factorization.

21105253 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2631.

The product of its (nonzero) digits is 300, while the sum is 19.

The square root of 21105253 is about 4594.0453850610. The cubic root of 21105253 is about 276.3525783547.

Adding to 21105253 its reverse (35250112), we get a palindrome (56355365).

The spelling of 21105253 in words is "twenty-one million, one hundred five thousand, two hundred fifty-three".