681977 has 2 divisors, whose sum is σ = 681978. Its totient is φ = 681976.

The previous prime is 681971. The next prime is 681979. The reversal of 681977 is 779186.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 440896 + 241081 = 664^2 + 491^2 .

It is a cyclic number.

It is not a de Polignac number, because 681977 - 2⁶ = 681913 is a prime.

Together with 681979, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 681977.

It is not a weakly prime, because it can be changed into another prime (681971) 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 as a sum of consecutive naturals, namely, 340988 + 340989.

It is an arithmetic number, because the mean of its divisors is an integer number (340989).

2⁶⁸¹⁹⁷⁷ is an apocalyptic number.

It is an amenable number.

681977 is a deficient number, since it is larger than the sum of its proper divisors (1).

681977 is an equidigital number, since it uses as much as digits as its factorization.

681977 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 21168, while the sum is 38.

The square root of 681977 is about 825.8189874301. The cubic root of 681977 is about 88.0217318917.

The spelling of 681977 in words is "six hundred eighty-one thousand, nine hundred seventy-seven".