78440291 has 2 divisors, whose sum is σ = 78440292. Its totient is φ = 78440290.

The previous prime is 78440287. The next prime is 78440357. The reversal of 78440291 is 19204487.

It is a weak prime.

It is an emirp because it is prime and its reverse (19204487) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 78440291 - 2² = 78440287 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (78440221) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39220145 + 39220146.

It is an arithmetic number, because the mean of its divisors is an integer number (39220146).

Almost surely, 2^78440291 is an apocalyptic number.

78440291 is a deficient number, since it is larger than the sum of its proper divisors (1).

78440291 is an equidigital number, since it uses as much as digits as its factorization.

78440291 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 16128, while the sum is 35.

The square root of 78440291 is about 8856.6523585382. The cubic root of 78440291 is about 428.0682974685.

The spelling of 78440291 in words is "seventy-eight million, four hundred forty thousand, two hundred ninety-one".