78309931 has 4 divisors (see below), whose sum is σ = 89497072. Its totient is φ = 67122792.

The previous prime is 78309929. The next prime is 78309941. The reversal of 78309931 is 13990387.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 13990387 = 103 ⋅135829.

It is a cyclic number.

It is not a de Polignac number, because 78309931 - 2¹ = 78309929 is a prime.

It is a super-2 number, since 2×78309931² = 12264890586449522, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (78309911) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5593560 + ... + 5593573.

It is an arithmetic number, because the mean of its divisors is an integer number (22374268).

Almost surely, 2^78309931 is an apocalyptic number.

78309931 is a deficient number, since it is larger than the sum of its proper divisors (11187141).

78309931 is a wasteful number, since it uses less digits than its factorization.

78309931 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11187140.

The product of its (nonzero) digits is 40824, while the sum is 40.

The square root of 78309931 is about 8849.2898585141. The cubic root of 78309931 is about 427.8310302676.

The spelling of 78309931 in words is "seventy-eight million, three hundred nine thousand, nine hundred thirty-one".