8457821 has 4 divisors (see below), whose sum is σ = 8749500. Its totient is φ = 8166144.

The previous prime is 8457811. The next prime is 8457847. The reversal of 8457821 is 1287548.

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

It can be written as a sum of positive squares in 2 ways, for example, as 7214596 + 1243225 = 2686^2 + 1115^2 .

It is a cyclic number.

It is not a de Polignac number, because 8457821 - 2¹⁰ = 8456797 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (8457811) 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, 145796 + ... + 145853.

It is an arithmetic number, because the mean of its divisors is an integer number (2187375).

Almost surely, 2^8457821 is an apocalyptic number.

It is an amenable number.

8457821 is a deficient number, since it is larger than the sum of its proper divisors (291679).

8457821 is a wasteful number, since it uses less digits than its factorization.

8457821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 291678.

The product of its digits is 17920, while the sum is 35.

The square root of 8457821 is about 2908.2333125112. The cubic root of 8457821 is about 203.7446263026.

The spelling of 8457821 in words is "eight million, four hundred fifty-seven thousand, eight hundred twenty-one".