771991 has 4 divisors (see below), whose sum is σ = 842184. Its totient is φ = 701800.

The previous prime is 771973. The next prime is 771997. The reversal of 771991 is 199177.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 771991 - 2⁷ = 771863 is a prime.

It is a Duffinian number.

771991 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (771997) 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 3 ways as a sum of consecutive naturals, for example, 35080 + ... + 35101.

It is an arithmetic number, because the mean of its divisors is an integer number (210546).

2⁷⁷¹⁹⁹¹ is an apocalyptic number.

771991 is a deficient number, since it is larger than the sum of its proper divisors (70193).

771991 is a wasteful number, since it uses less digits than its factorization.

771991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 70192.

The product of its digits is 3969, while the sum is 34.

The square root of 771991 is about 878.6301838658. The cubic root of 771991 is about 91.7354957806.

The spelling of 771991 in words is "seven hundred seventy-one thousand, nine hundred ninety-one".