681000391 has 4 divisors (see below), whose sum is σ = 681055312. Its totient is φ = 680945472.

The previous prime is 681000389. The next prime is 681000407. The reversal of 681000391 is 193000186.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 193000186 = 2 ⋅96500093.

It is a cyclic number.

It is not a de Polignac number, because 681000391 - 2¹ = 681000389 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (681000371) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 910 + ... + 36916.

It is an arithmetic number, because the mean of its divisors is an integer number (170263828).

Almost surely, 2^681000391 is an apocalyptic number.

681000391 is a deficient number, since it is larger than the sum of its proper divisors (54921).

681000391 is a wasteful number, since it uses less digits than its factorization.

681000391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 54920.

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

The square root of 681000391 is about 26095.9841929750. The cubic root of 681000391 is about 879.7969534120.

The spelling of 681000391 in words is "six hundred eighty-one million, three hundred ninety-one", and thus it is an aban number.