78516781 has 4 divisors (see below), whose sum is σ = 89733472. Its totient is φ = 67300092.

The previous prime is 78516773. The next prime is 78516793. The reversal of 78516781 is 18761587.

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.

It is a cyclic number.

It is not a de Polignac number, because 78516781 - 2³ = 78516773 is a prime.

It is a super-2 number, since 2×78516781² = 12329769797203922, 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 (78516281) 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, 5608335 + ... + 5608348.

It is an arithmetic number, because the mean of its divisors is an integer number (22433368).

Almost surely, 2^78516781 is an apocalyptic number.

It is an amenable number.

78516781 is a deficient number, since it is larger than the sum of its proper divisors (11216691).

78516781 is a wasteful number, since it uses less digits than its factorization.

78516781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11216690.

The product of its digits is 94080, while the sum is 43.

The square root of 78516781 is about 8860.9695293461. The cubic root of 78516781 is about 428.2073939561.

It can be divided in two parts, 78516 and 781, that added together give a palindrome (79297).

The spelling of 78516781 in words is "seventy-eight million, five hundred sixteen thousand, seven hundred eighty-one".