21040253 has 4 divisors (see below), whose sum is σ = 22658748. Its totient is φ = 19421760.

The previous prime is 21040249. The next prime is 21040267. The reversal of 21040253 is 35204012.

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

It can be written as a sum of positive squares in 2 ways, for example, as 10004569 + 11035684 = 3163^2 + 3322^2 .

It is a cyclic number.

It is not a de Polignac number, because 21040253 - 2² = 21040249 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 (21040213) 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 3 ways as a sum of consecutive naturals, for example, 809228 + ... + 809253.

It is an arithmetic number, because the mean of its divisors is an integer number (5664687).

Almost surely, 2^21040253 is an apocalyptic number.

It is an amenable number.

21040253 is a deficient number, since it is larger than the sum of its proper divisors (1618495).

21040253 is a wasteful number, since it uses less digits than its factorization.

21040253 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1618494.

The product of its (nonzero) digits is 240, while the sum is 17.

The square root of 21040253 is about 4586.9655546995. The cubic root of 21040253 is about 276.0685828655.

Adding to 21040253 its reverse (35204012), we get a palindrome (56244265).

The spelling of 21040253 in words is "twenty-one million, forty thousand, two hundred fifty-three".