78399639 has 6 divisors (see below), whose sum is σ = 113243936. Its totient is φ = 52266420.

The previous prime is 78399637. The next prime is 78399647. The reversal of 78399639 is 93699387.

It is not a de Polignac number, because 78399639 - 2¹ = 78399637 is a prime.

It is a super-2 number, since 2×78399639² = 12293006790660642, 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 (78399637) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 4355527 + ... + 4355544.

Almost surely, 2^78399639 is an apocalyptic number.

78399639 is a deficient number, since it is larger than the sum of its proper divisors (34844297).

78399639 is a wasteful number, since it uses less digits than its factorization.

78399639 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8711077 (or 8711074 counting only the distinct ones).

The product of its digits is 2204496, while the sum is 54.

The square root of 78399639 is about 8854.3570630509. The cubic root of 78399639 is about 427.9943353109.

The spelling of 78399639 in words is "seventy-eight million, three hundred ninety-nine thousand, six hundred thirty-nine".