77985991 has 2 divisors, whose sum is σ = 77985992. Its totient is φ = 77985990.

The previous prime is 77985979. The next prime is 77985997. The reversal of 77985991 is 19958977.

It is a strong prime.

It is an emirp because it is prime and its reverse (19958977) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 77985991 - 2¹³ = 77977799 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 (77985997) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 38992995 + 38992996.

It is an arithmetic number, because the mean of its divisors is an integer number (38992996).

Almost surely, 2^77985991 is an apocalyptic number.

77985991 is a deficient number, since it is larger than the sum of its proper divisors (1).

77985991 is an equidigital number, since it uses as much as digits as its factorization.

77985991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1428840, while the sum is 55.

The square root of 77985991 is about 8830.9677272652. The cubic root of 77985991 is about 427.2402872898.

The spelling of 77985991 in words is "seventy-seven million, nine hundred eighty-five thousand, nine hundred ninety-one".