77920991 has 2 divisors, whose sum is σ = 77920992. Its totient is φ = 77920990.

The previous prime is 77920903. The next prime is 77920993. The reversal of 77920991 is 19902977.

It is a strong prime.

It is an emirp because it is prime and its reverse (19902977) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 77920991 - 2²⁶ = 10812127 is a prime.

Together with 77920993, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (77920993) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 38960495 + 38960496.

It is an arithmetic number, because the mean of its divisors is an integer number (38960496).

Almost surely, 2^77920991 is an apocalyptic number.

77920991 is a deficient number, since it is larger than the sum of its proper divisors (1).

77920991 is an equidigital number, since it uses as much as digits as its factorization.

77920991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 71442, while the sum is 44.

The square root of 77920991 is about 8827.2867292277. The cubic root of 77920991 is about 427.1215551203.

The spelling of 77920991 in words is "seventy-seven million, nine hundred twenty thousand, nine hundred ninety-one".