78861866 has 4 divisors (see below), whose sum is σ = 118292802. Its totient is φ = 39430932.

The previous prime is 78861859. The next prime is 78861899. The reversal of 78861866 is 66816887.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 66816887 = 487 ⋅137201.

It can be written as a sum of positive squares in only one way, i.e., 48930025 + 29931841 = 6995^2 + 5471^2 .

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 as a sum of consecutive naturals, namely, 19715465 + ... + 19715468.

Almost surely, 2^78861866 is an apocalyptic number.

78861866 is a deficient number, since it is larger than the sum of its proper divisors (39430936).

78861866 is a wasteful number, since it uses less digits than its factorization.

78861866 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39430935.

The product of its digits is 774144, while the sum is 50.

The square root of 78861866 is about 8880.4203729328. The cubic root of 78861866 is about 428.8338077889.

The spelling of 78861866 in words is "seventy-eight million, eight hundred sixty-one thousand, eight hundred sixty-six".