2780021 has 4 divisors (see below), whose sum is σ = 2827200. Its totient is φ = 2732844.

The previous prime is 2779991. The next prime is 2780039. The reversal of 2780021 is 1200872.

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 2780021 - 2¹⁸ = 2517877 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 2779975 and 2780002.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2780521) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 23501 + ... + 23618.

It is an arithmetic number, because the mean of its divisors is an integer number (706800).

2^2780021 is an apocalyptic number.

It is an amenable number.

2780021 is a deficient number, since it is larger than the sum of its proper divisors (47179).

2780021 is an equidigital number, since it uses as much as digits as its factorization.

2780021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 47178.

The product of its (nonzero) digits is 224, while the sum is 20.

The square root of 2780021 is about 1667.3394975229. The cubic root of 2780021 is about 140.6099408401.

Adding to 2780021 its reverse (1200872), we get a palindrome (3980893).

The spelling of 2780021 in words is "two million, seven hundred eighty thousand, twenty-one".