2809978 has 4 divisors (see below), whose sum is σ = 4214970. Its totient is φ = 1404988.

The previous prime is 2809973. The next prime is 2809987. The reversal of 2809978 is 8799082.

2809978 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 8799082 = 2 ⋅4399541.

It can be written as a sum of positive squares in only one way, i.e., 2582449 + 227529 = 1607^2 + 477^2 .

It is an Ulam number.

It is not an unprimeable number, because it can be changed into a prime (2809973) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 702493 + ... + 702496.

2^2809978 is an apocalyptic number.

2809978 is a deficient number, since it is larger than the sum of its proper divisors (1404992).

2809978 is a wasteful number, since it uses less digits than its factorization.

2809978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1404991.

The product of its (nonzero) digits is 72576, while the sum is 43.

The square root of 2809978 is about 1676.2988993613. The cubic root of 2809978 is about 141.1131998414.

The spelling of 2809978 in words is "two million, eight hundred nine thousand, nine hundred seventy-eight".