21057571 has 4 divisors (see below), whose sum is σ = 21067200. Its totient is φ = 21047944.

The previous prime is 21057563. The next prime is 21057599. The reversal of 21057571 is 17575012.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21057571 - 2³ = 21057563 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21057511) 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, 225 + ... + 6493.

It is an arithmetic number, because the mean of its divisors is an integer number (5266800).

Almost surely, 2^21057571 is an apocalyptic number.

21057571 is a deficient number, since it is larger than the sum of its proper divisors (9629).

21057571 is an equidigital number, since it uses as much as digits as its factorization.

21057571 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9628.

The product of its (nonzero) digits is 2450, while the sum is 28.

The square root of 21057571 is about 4588.8529067731. The cubic root of 21057571 is about 276.1443050950.

The spelling of 21057571 in words is "twenty-one million, fifty-seven thousand, five hundred seventy-one".