78131917 has 2 divisors, whose sum is σ = 78131918. Its totient is φ = 78131916.

The previous prime is 78131909. The next prime is 78131927. The reversal of 78131917 is 71913187.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 50893956 + 27237961 = 7134^2 + 5219^2 .

It is a cyclic number.

It is not a de Polignac number, because 78131917 - 2³ = 78131909 is a prime.

It is a super-2 number, since 2×78131917² = 12209192908189778, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78131927) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39065958 + 39065959.

It is an arithmetic number, because the mean of its divisors is an integer number (39065959).

Almost surely, 2^78131917 is an apocalyptic number.

It is an amenable number.

78131917 is a deficient number, since it is larger than the sum of its proper divisors (1).

78131917 is an equidigital number, since it uses as much as digits as its factorization.

78131917 is an evil number, because the sum of its binary digits is even.

The product of its digits is 10584, while the sum is 37.

The square root of 78131917 is about 8839.2260407798. The cubic root of 78131917 is about 427.5066027274.

It can be divided in two parts, 7813 and 1917, that added together give a triangular number (9730 = T₁₃₉).

The spelling of 78131917 in words is "seventy-eight million, one hundred thirty-one thousand, nine hundred seventeen".