681979 has 2 divisors, whose sum is σ = 681980. Its totient is φ = 681978.

The previous prime is 681977. The next prime is 681983. The reversal of 681979 is 979186.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 681979 - 2¹ = 681977 is a prime.

Together with 681977, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (681971) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 340989 + 340990.

It is an arithmetic number, because the mean of its divisors is an integer number (340990).

2⁶⁸¹⁹⁷⁹ is an apocalyptic number.

681979 is a deficient number, since it is larger than the sum of its proper divisors (1).

681979 is an equidigital number, since it uses as much as digits as its factorization.

681979 is an evil number, because the sum of its binary digits is even.

The product of its digits is 27216, while the sum is 40.

The square root of 681979 is about 825.8201983483. The cubic root of 681979 is about 88.0218179373.

The spelling of 681979 in words is "six hundred eighty-one thousand, nine hundred seventy-nine".