78439815 has 24 divisors (see below), whose sum is σ = 139639968. Its totient is φ = 40703040.

The previous prime is 78439813. The next prime is 78439859. The reversal of 78439815 is 51893487.

It is not a de Polignac number, because 78439815 - 2¹ = 78439813 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (78439813) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 21891 + ... + 25220.

It is an arithmetic number, because the mean of its divisors is an integer number (5818332).

Almost surely, 2^78439815 is an apocalyptic number.

78439815 is a deficient number, since it is larger than the sum of its proper divisors (61200153).

78439815 is a wasteful number, since it uses less digits than its factorization.

78439815 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 47159 (or 47156 counting only the distinct ones).

The product of its digits is 241920, while the sum is 45.

The square root of 78439815 is about 8856.6254860415. The cubic root of 78439815 is about 428.0674315830.

The spelling of 78439815 in words is "seventy-eight million, four hundred thirty-nine thousand, eight hundred fifteen".