4256821 has 4 divisors (see below), whose sum is σ = 4308192. Its totient is φ = 4205452.

The previous prime is 4256807. The next prime is 4256831. The reversal of 4256821 is 1286524.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 4256821 - 2²¹ = 2159669 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 4256821.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (4256831) 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, 25561 + ... + 25726.

It is an arithmetic number, because the mean of its divisors is an integer number (1077048).

Almost surely, 2^4256821 is an apocalyptic number.

It is an amenable number.

4256821 is a deficient number, since it is larger than the sum of its proper divisors (51371).

4256821 is an equidigital number, since it uses as much as digits as its factorization.

4256821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 51370.

The product of its digits is 3840, while the sum is 28.

The square root of 4256821 is about 2063.2064850615. The cubic root of 4256821 is about 162.0672001853.

The spelling of 4256821 in words is "four million, two hundred fifty-six thousand, eight hundred twenty-one".