21126571 has 4 divisors (see below), whose sum is σ = 21381192. Its totient is φ = 20871952.

The previous prime is 21126569. The next prime is 21126583. The reversal of 21126571 is 17562112.

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 21126571 - 2¹ = 21126569 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21126551) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 127186 + ... + 127351.

It is an arithmetic number, because the mean of its divisors is an integer number (5345298).

Almost surely, 2^21126571 is an apocalyptic number.

21126571 is a deficient number, since it is larger than the sum of its proper divisors (254621).

21126571 is an equidigital number, since it uses as much as digits as its factorization.

21126571 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 254620.

The product of its digits is 840, while the sum is 25.

The square root of 21126571 is about 4596.3649768050. The cubic root of 21126571 is about 276.4455931415.

Adding to 21126571 its reverse (17562112), we get a palindrome (38688683).

The spelling of 21126571 in words is "twenty-one million, one hundred twenty-six thousand, five hundred seventy-one".