78688781 has 4 divisors (see below), whose sum is σ = 78708732. Its totient is φ = 78668832.

The previous prime is 78688769. The next prime is 78688783. The reversal of 78688781 is 18788687.

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: 18788687 = 977 ⋅19231.

It can be written as a sum of positive squares in 2 ways, for example, as 17926756 + 60762025 = 4234^2 + 7795^2 .

It is a cyclic number.

It is not a de Polignac number, because 78688781 - 2¹⁰ = 78687757 is a prime.

It is a super-2 number, since 2×78688781² = 12383848510531922, 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 (78688783) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1856 + ... + 12681.

It is an arithmetic number, because the mean of its divisors is an integer number (19677183).

Almost surely, 2^78688781 is an apocalyptic number.

It is an amenable number.

78688781 is a deficient number, since it is larger than the sum of its proper divisors (19951).

78688781 is a wasteful number, since it uses less digits than its factorization.

78688781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19950.

The product of its digits is 1204224, while the sum is 53.

The square root of 78688781 is about 8870.6697041430. The cubic root of 78688781 is about 428.5198450244.

The spelling of 78688781 in words is "seventy-eight million, six hundred eighty-eight thousand, seven hundred eighty-one".