78780991 has 2 divisors, whose sum is σ = 78780992. Its totient is φ = 78780990.

The previous prime is 78780983. The next prime is 78781019. The reversal of 78780991 is 19908787.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 78780991 - 2³ = 78780983 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78780901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39390495 + 39390496.

It is an arithmetic number, because the mean of its divisors is an integer number (39390496).

Almost surely, 2^78780991 is an apocalyptic number.

78780991 is a deficient number, since it is larger than the sum of its proper divisors (1).

78780991 is an equidigital number, since it uses as much as digits as its factorization.

78780991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 254016, while the sum is 49.

The square root of 78780991 is about 8875.8656479242. The cubic root of 78780991 is about 428.6871640498.

The spelling of 78780991 in words is "seventy-eight million, seven hundred eighty thousand, nine hundred ninety-one".