78258781 has 4 divisors (see below), whose sum is σ = 78537564. Its totient is φ = 77980000.

The previous prime is 78258779. The next prime is 78258809. The reversal of 78258781 is 18785287.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 18785287 = 31 ⋅605977.

It can be written as a sum of positive squares in 2 ways, for example, as 25100100 + 53158681 = 5010^2 + 7291^2 .

It is a cyclic number.

It is not a de Polignac number, because 78258781 - 2¹ = 78258779 is a prime.

It is a super-2 number, since 2×78258781² = 12248873607211922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (78258281) 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, 138970 + ... + 139531.

It is an arithmetic number, because the mean of its divisors is an integer number (19634391).

Almost surely, 2^78258781 is an apocalyptic number.

It is an amenable number.

78258781 is a deficient number, since it is larger than the sum of its proper divisors (278783).

78258781 is a wasteful number, since it uses less digits than its factorization.

78258781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 278782.

The product of its digits is 250880, while the sum is 46.

The square root of 78258781 is about 8846.3993240188. The cubic root of 78258781 is about 427.7378606307.

The spelling of 78258781 in words is "seventy-eight million, two hundred fifty-eight thousand, seven hundred eighty-one".