78638665 has 16 divisors (see below), whose sum is σ = 108321408. Its totient is φ = 53686656.

The previous prime is 78638647. The next prime is 78638669. The reversal of 78638665 is 56683687.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 78638665 - 2²³ = 70250057 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (78638669) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3334 + ... + 12976.

It is an arithmetic number, because the mean of its divisors is an integer number (6770088).

Almost surely, 2^78638665 is an apocalyptic number.

It is an amenable number.

78638665 is a deficient number, since it is larger than the sum of its proper divisors (29682743).

78638665 is a wasteful number, since it uses less digits than its factorization.

78638665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9888.

The product of its digits is 1451520, while the sum is 49.

The square root of 78638665 is about 8867.8444393212. The cubic root of 78638665 is about 428.4288525470.

The spelling of 78638665 in words is "seventy-eight million, six hundred thirty-eight thousand, six hundred sixty-five".