78117818 has 4 divisors (see below), whose sum is σ = 117176730. Its totient is φ = 39058908.

The previous prime is 78117817. The next prime is 78117859. The reversal of 78117818 is 81871187.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 49098049 + 29019769 = 7007^2 + 5387^2 .

It is a super-2 number, since 2×78117818² = 12204786978162248, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (78117817) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 19529453 + ... + 19529456.

Almost surely, 2^78117818 is an apocalyptic number.

78117818 is a deficient number, since it is larger than the sum of its proper divisors (39058912).

78117818 is a wasteful number, since it uses less digits than its factorization.

78117818 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 39058911.

The product of its digits is 25088, while the sum is 41.

The square root of 78117818 is about 8838.4284802220. The cubic root of 78117818 is about 427.4808864840.

The spelling of 78117818 in words is "seventy-eight million, one hundred seventeen thousand, eight hundred eighteen".