78820409 has 6 divisors (see below), whose sum is σ = 80791470. Its totient is φ = 76896320.

The previous prime is 78820393. The next prime is 78820439. The reversal of 78820409 is 90402887.

It can be written as a sum of positive squares in 3 ways, for example, as 2310400 + 76510009 = 1520^2 + 8747^2 .

It is not a de Polignac number, because 78820409 - 2⁴ = 78820393 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (78820439) 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 5 ways as a sum of consecutive naturals, for example, 21764 + ... + 25125.

It is an arithmetic number, because the mean of its divisors is an integer number (13465245).

Almost surely, 2^78820409 is an apocalyptic number.

It is an amenable number.

78820409 is a deficient number, since it is larger than the sum of its proper divisors (1971061).

78820409 is an equidigital number, since it uses as much as digits as its factorization.

78820409 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 46971 (or 46930 counting only the distinct ones).

The product of its (nonzero) digits is 32256, while the sum is 38.

The square root of 78820409 is about 8878.0858860455. The cubic root of 78820409 is about 428.7586498778.

The spelling of 78820409 in words is "seventy-eight million, eight hundred twenty thousand, four hundred nine".