78391265 has 4 divisors (see below), whose sum is σ = 94069524. Its totient is φ = 62713008.

The previous prime is 78391249. The next prime is 78391297. The reversal of 78391265 is 56219387.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 56219387 = 7 ⋅8031341.

It can be written as a sum of positive squares in 2 ways, for example, as 54878464 + 23512801 = 7408^2 + 4849^2 .

It is a cyclic number.

It is not a de Polignac number, because 78391265 - 2⁴ = 78391249 is a prime.

It is a super-2 number, since 2×78391265² = 12290380856600450, which contains 22 as substring.

It is a Duffinian number.

It is an unprimeable number.

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 3 ways as a sum of consecutive naturals, for example, 7839122 + ... + 7839131.

It is an arithmetic number, because the mean of its divisors is an integer number (23517381).

Almost surely, 2^78391265 is an apocalyptic number.

It is an amenable number.

78391265 is a deficient number, since it is larger than the sum of its proper divisors (15678259).

78391265 is a wasteful number, since it uses less digits than its factorization.

78391265 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15678258.

The product of its digits is 90720, while the sum is 41.

The square root of 78391265 is about 8853.8841758857. The cubic root of 78391265 is about 427.9790964985.

The spelling of 78391265 in words is "seventy-eight million, three hundred ninety-one thousand, two hundred sixty-five".