21811253 has 4 divisors (see below), whose sum is σ = 22027308. Its totient is φ = 21595200.

The previous prime is 21811211. The next prime is 21811261. The reversal of 21811253 is 35211812.

It is a happy number.

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 13557124 + 8254129 = 3682^2 + 2873^2 .

It is a cyclic number.

It is not a de Polignac number, because 21811253 - 2¹² = 21807157 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 (21810253) 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, 107876 + ... + 108077.

It is an arithmetic number, because the mean of its divisors is an integer number (5506827).

Almost surely, 2^21811253 is an apocalyptic number.

It is an amenable number.

21811253 is a deficient number, since it is larger than the sum of its proper divisors (216055).

21811253 is a wasteful number, since it uses less digits than its factorization.

21811253 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 216054.

The product of its digits is 480, while the sum is 23.

The square root of 21811253 is about 4670.2519204000. The cubic root of 21811253 is about 279.4003023826.

The spelling of 21811253 in words is "twenty-one million, eight hundred eleven thousand, two hundred fifty-three".