78057209 has 4 divisors (see below), whose sum is σ = 78074880. Its totient is φ = 78039540.

The previous prime is 78057179. The next prime is 78057223. The reversal of 78057209 is 90275087.

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.

It is a cyclic number.

It is not a de Polignac number, because 78057209 - 2²⁴ = 61279993 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (78057229) 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, 4412 + ... + 13250.

It is an arithmetic number, because the mean of its divisors is an integer number (19518720).

Almost surely, 2^78057209 is an apocalyptic number.

It is an amenable number.

78057209 is a deficient number, since it is larger than the sum of its proper divisors (17671).

78057209 is an equidigital number, since it uses as much as digits as its factorization.

78057209 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17670.

The product of its (nonzero) digits is 35280, while the sum is 38.

The square root of 78057209 is about 8834.9990945104. Note that the first 3 decimals coincide. The cubic root of 78057209 is about 427.3703018428.

The spelling of 78057209 in words is "seventy-eight million, fifty-seven thousand, two hundred nine".