78991111 has 2 divisors, whose sum is σ = 78991112. Its totient is φ = 78991110.

The previous prime is 78991103. The next prime is 78991117. The reversal of 78991111 is 11119987.

It is a strong prime.

It is an emirp because it is prime and its reverse (11119987) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 78991111 - 2³ = 78991103 is a prime.

It is equal to p_4613986 and since 78991111 and 4613986 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78991117) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39495555 + 39495556.

It is an arithmetic number, because the mean of its divisors is an integer number (39495556).

Almost surely, 2^78991111 is an apocalyptic number.

78991111 is a deficient number, since it is larger than the sum of its proper divisors (1).

78991111 is an equidigital number, since it uses as much as digits as its factorization.

78991111 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4536, while the sum is 37.

The square root of 78991111 is about 8887.6943579311. The cubic root of 78991111 is about 429.0679487317.

The spelling of 78991111 in words is "seventy-eight million, nine hundred ninety-one thousand, one hundred eleven".