21071243 has 4 divisors (see below), whose sum is σ = 21987408. Its totient is φ = 20155080.

The previous prime is 21071221. The next prime is 21071249. The reversal of 21071243 is 34217012.

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

It is a cyclic number.

It is not a de Polignac number, because 21071243 - 2⁶ = 21071179 is a prime.

It is a Duffinian number.

It is a plaindrome in base 13.

It is a zygodrome in base 13.

It is not an unprimeable number, because it can be changed into a prime (21071249) 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, 458048 + ... + 458093.

It is an arithmetic number, because the mean of its divisors is an integer number (5496852).

Almost surely, 2^21071243 is an apocalyptic number.

21071243 is a gapful number since it is divisible by the number (23) formed by its first and last digit.

21071243 is a deficient number, since it is larger than the sum of its proper divisors (916165).

21071243 is an equidigital number, since it uses as much as digits as its factorization.

21071243 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 916164.

The product of its (nonzero) digits is 336, while the sum is 20.

The square root of 21071243 is about 4590.3423619595. The cubic root of 21071243 is about 276.2040560217.

Adding to 21071243 its reverse (34217012), we get a palindrome (55288255).

The spelling of 21071243 in words is "twenty-one million, seventy-one thousand, two hundred forty-three".