681555851 has 2 divisors, whose sum is σ = 681555852. Its totient is φ = 681555850.

The previous prime is 681555793. The next prime is 681555893. The reversal of 681555851 is 158555186.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-681555851 is a prime.

It is not a weakly prime, because it can be changed into another prime (681555451) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 340777925 + 340777926.

It is an arithmetic number, because the mean of its divisors is an integer number (340777926).

Almost surely, 2^681555851 is an apocalyptic number.

681555851 is a deficient number, since it is larger than the sum of its proper divisors (1).

681555851 is an equidigital number, since it uses as much as digits as its factorization.

681555851 is an evil number, because the sum of its binary digits is even.

The product of its digits is 240000, while the sum is 44.

The square root of 681555851 is about 26106.6246573547. The cubic root of 681555851 is about 880.0360914089.

The spelling of 681555851 in words is "six hundred eighty-one million, five hundred fifty-five thousand, eight hundred fifty-one".