78566909 has 4 divisors (see below), whose sum is σ = 78584640. Its totient is φ = 78549180.

The previous prime is 78566903. The next prime is 78566921. The reversal of 78566909 is 90966587.

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, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 90966587 = 23 ⋅3955069.

It is a cyclic number.

It is not a de Polignac number, because 78566909 - 2¹⁶ = 78501373 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 (78566903) 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, 4214 + ... + 13224.

It is an arithmetic number, because the mean of its divisors is an integer number (19646160).

Almost surely, 2^78566909 is an apocalyptic number.

It is an amenable number.

78566909 is a deficient number, since it is larger than the sum of its proper divisors (17731).

78566909 is an equidigital number, since it uses as much as digits as its factorization.

78566909 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17730.

The product of its (nonzero) digits is 816480, while the sum is 50.

The square root of 78566909 is about 8863.7976624018. The cubic root of 78566909 is about 428.2985023516.

The spelling of 78566909 in words is "seventy-eight million, five hundred sixty-six thousand, nine hundred nine".