2787821 has 4 divisors (see below), whose sum is σ = 2791932. Its totient is φ = 2783712.

The previous prime is 2787781. The next prime is 2787859. The reversal of 2787821 is 1287872.

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 2706025 + 81796 = 1645^2 + 286^2 .

It is a cyclic number.

It is not a de Polignac number, because 2787821 - 2¹⁴ = 2771437 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 (2787121) 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, 770 + ... + 2483.

It is an arithmetic number, because the mean of its divisors is an integer number (697983).

2^2787821 is an apocalyptic number.

It is an amenable number.

2787821 is a deficient number, since it is larger than the sum of its proper divisors (4111).

2787821 is an equidigital number, since it uses as much as digits as its factorization.

2787821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4110.

The product of its digits is 12544, while the sum is 35.

The square root of 2787821 is about 1669.6769148551. The cubic root of 2787821 is about 140.7413227490.

The spelling of 2787821 in words is "two million, seven hundred eighty-seven thousand, eight hundred twenty-one".