78399638 has 4 divisors (see below), whose sum is σ = 117599460. Its totient is φ = 39199818.

The previous prime is 78399637. The next prime is 78399647. The reversal of 78399638 is 83699387.

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

It is a super-2 number, since 2×78399638² = 12293006477062088, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 78399638.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (78399637) 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 as a sum of consecutive naturals, namely, 19599908 + ... + 19599911.

It is an arithmetic number, because the mean of its divisors is an integer number (29399865).

Almost surely, 2^78399638 is an apocalyptic number.

78399638 is a deficient number, since it is larger than the sum of its proper divisors (39199822).

78399638 is a wasteful number, since it uses less digits than its factorization.

78399638 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39199821.

The product of its digits is 1959552, while the sum is 53.

The square root of 78399638 is about 8854.3570065816. The cubic root of 78399638 is about 427.9943334912.

The spelling of 78399638 in words is "seventy-eight million, three hundred ninety-nine thousand, six hundred thirty-eight".