78317531 has 2 divisors, whose sum is σ = 78317532. Its totient is φ = 78317530.

The previous prime is 78317513. The next prime is 78317543. The reversal of 78317531 is 13571387.

Together with previous prime (78317513) it forms an Ormiston pair, because they use the same digits, order apart.

It is a strong prime.

It is an emirp because it is prime and its reverse (13571387) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 78317531 - 2¹⁰ = 78316507 is a prime.

It is a super-2 number, since 2×78317531² = 12267271323871922, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 78317491 and 78317500.

It is not a weakly prime, because it can be changed into another prime (78317581) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39158765 + 39158766.

It is an arithmetic number, because the mean of its divisors is an integer number (39158766).

Almost surely, 2^78317531 is an apocalyptic number.

78317531 is a deficient number, since it is larger than the sum of its proper divisors (1).

78317531 is an equidigital number, since it uses as much as digits as its factorization.

78317531 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 17640, while the sum is 35.

The square root of 78317531 is about 8849.7192610839. The cubic root of 78317531 is about 427.8448701923.

The spelling of 78317531 in words is "seventy-eight million, three hundred seventeen thousand, five hundred thirty-one".