681518639 has 2 divisors, whose sum is σ = 681518640. Its totient is φ = 681518638.

The previous prime is 681518623. The next prime is 681518711. The reversal of 681518639 is 936815186.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 681518639 - 2⁴ = 681518623 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 681518593 and 681518602.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (681518339) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 340759319 + 340759320.

It is an arithmetic number, because the mean of its divisors is an integer number (340759320).

Almost surely, 2^681518639 is an apocalyptic number.

681518639 is a deficient number, since it is larger than the sum of its proper divisors (1).

681518639 is an equidigital number, since it uses as much as digits as its factorization.

681518639 is an evil number, because the sum of its binary digits is even.

The product of its digits is 311040, while the sum is 47.

The square root of 681518639 is about 26105.9119549576. The cubic root of 681518639 is about 880.0200748692.

The spelling of 681518639 in words is "six hundred eighty-one million, five hundred eighteen thousand, six hundred thirty-nine".