21057171 has 4 divisors (see below), whose sum is σ = 28076232. Its totient is φ = 14038112.

The previous prime is 21057151. The next prime is 21057173. The reversal of 21057171 is 17175012.

It is a happy number.

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 21057171 - 2¹¹ = 21055123 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21057173) 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, 3509526 + ... + 3509531.

It is an arithmetic number, because the mean of its divisors is an integer number (7019058).

Almost surely, 2^21057171 is an apocalyptic number.

21057171 is a deficient number, since it is larger than the sum of its proper divisors (7019061).

21057171 is an equidigital number, since it uses as much as digits as its factorization.

21057171 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7019060.

The product of its (nonzero) digits is 490, while the sum is 24.

The square root of 21057171 is about 4588.8093226893. The cubic root of 21057171 is about 276.1425565803.

The spelling of 21057171 in words is "twenty-one million, fifty-seven thousand, one hundred seventy-one".