21253873 has 4 divisors (see below), whose sum is σ = 21828340. Its totient is φ = 20679408.

The previous prime is 21253871. The next prime is 21253889. The reversal of 21253873 is 37835212.

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 12054784 + 9199089 = 3472^2 + 3033^2 .

It is a cyclic number.

It is not a de Polignac number, because 21253873 - 2¹ = 21253871 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21253871) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 287178 + ... + 287251.

It is an arithmetic number, because the mean of its divisors is an integer number (5457085).

Almost surely, 2^21253873 is an apocalyptic number.

It is an amenable number.

21253873 is a deficient number, since it is larger than the sum of its proper divisors (574467).

21253873 is an equidigital number, since it uses as much as digits as its factorization.

21253873 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 574466.

The product of its digits is 10080, while the sum is 31.

The square root of 21253873 is about 4610.1922953387. The cubic root of 21253873 is about 276.9997393421. Note that the first 3 decimals are identical.

The spelling of 21253873 in words is "twenty-one million, two hundred fifty-three thousand, eight hundred seventy-three".