28215571 has 4 divisors (see below), whose sum is σ = 28978192. Its totient is φ = 27452952.

The previous prime is 28215559. The next prime is 28215599. The reversal of 28215571 is 17551282.

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 28215571 - 2⁹ = 28215059 is a prime.

It is a super-2 number, since 2×28215571² = 1592236893712082, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28215541) 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, 381255 + ... + 381328.

It is an arithmetic number, because the mean of its divisors is an integer number (7244548).

Almost surely, 2^28215571 is an apocalyptic number.

28215571 is a deficient number, since it is larger than the sum of its proper divisors (762621).

28215571 is an equidigital number, since it uses as much as digits as its factorization.

28215571 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 762620.

The product of its digits is 5600, while the sum is 31.

The square root of 28215571 is about 5311.8331110832. The cubic root of 28215571 is about 304.4361921335.

The spelling of 28215571 in words is "twenty-eight million, two hundred fifteen thousand, five hundred seventy-one".