681555839 has 4 divisors (see below), whose sum is σ = 682216656. Its totient is φ = 680895024.

The previous prime is 681555793. The next prime is 681555851. The reversal of 681555839 is 938555186.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-681555839 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 (681555899) 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, 328859 + ... + 330924.

It is an arithmetic number, because the mean of its divisors is an integer number (170554164).

Almost surely, 2^681555839 is an apocalyptic number.

681555839 is a deficient number, since it is larger than the sum of its proper divisors (660817).

681555839 is a wasteful number, since it uses less digits than its factorization.

681555839 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 660816.

The product of its digits is 1296000, while the sum is 50.

The square root of 681555839 is about 26106.6244275280. The cubic root of 681555839 is about 880.0360862440.

The spelling of 681555839 in words is "six hundred eighty-one million, five hundred fifty-five thousand, eight hundred thirty-nine".