21171243 has 4 divisors (see below), whose sum is σ = 28228328. Its totient is φ = 14114160.

The previous prime is 21171217. The next prime is 21171251. The reversal of 21171243 is 34217112.

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

It is not a de Polignac number, because 21171243 - 2⁸ = 21170987 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21171203) 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, 3528538 + ... + 3528543.

It is an arithmetic number, because the mean of its divisors is an integer number (7057082).

Almost surely, 2^21171243 is an apocalyptic number.

21171243 is a deficient number, since it is larger than the sum of its proper divisors (7057085).

21171243 is an equidigital number, since it uses as much as digits as its factorization.

21171243 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7057084.

The product of its digits is 336, while the sum is 21.

The square root of 21171243 is about 4601.2219029297. The cubic root of 21171243 is about 276.6403034508.

Adding to 21171243 its reverse (34217112), we get a palindrome (55388355).

The spelling of 21171243 in words is "twenty-one million, one hundred seventy-one thousand, two hundred forty-three".