681391 has 4 divisors (see below), whose sum is σ = 693000. Its totient is φ = 669784.

The previous prime is 681371. The next prime is 681403. The reversal of 681391 is 193186.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 681391 - 2⁹ = 680879 is a prime.

It is a Duffinian number.

681391 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (681311) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5716 + ... + 5833.

It is an arithmetic number, because the mean of its divisors is an integer number (173250).

2⁶⁸¹³⁹¹ is an apocalyptic number.

681391 is a deficient number, since it is larger than the sum of its proper divisors (11609).

681391 is a wasteful number, since it uses less digits than its factorization.

681391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11608.

The product of its digits is 1296, while the sum is 28.

The square root of 681391 is about 825.4641118789. The cubic root of 681391 is about 87.9965132916.

The spelling of 681391 in words is "six hundred eighty-one thousand, three hundred ninety-one".