78121791 has 12 divisors (see below), whose sum is σ = 123101160. Its totient is φ = 47346480.

The previous prime is 78121781. The next prime is 78121793. The reversal of 78121791 is 19712187.

It is not a de Polignac number, because 78121791 - 2⁶ = 78121727 is a prime.

It is a super-2 number, since 2×78121791² = 12206028458095362, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (78121793) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 394456 + ... + 394653.

It is an arithmetic number, because the mean of its divisors is an integer number (10258430).

Almost surely, 2^78121791 is an apocalyptic number.

78121791 is a deficient number, since it is larger than the sum of its proper divisors (44979369).

78121791 is a wasteful number, since it uses less digits than its factorization.

78121791 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 789126 (or 789123 counting only the distinct ones).

The product of its digits is 7056, while the sum is 36.

The square root of 78121791 is about 8838.6532345149. The cubic root of 78121791 is about 427.4881334554.

The spelling of 78121791 in words is "seventy-eight million, one hundred twenty-one thousand, seven hundred ninety-one".