687636709 has 2 divisors, whose sum is σ = 687636710. Its totient is φ = 687636708.

The previous prime is 687636701. The next prime is 687636731. The reversal of 687636709 is 907636786.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 683822500 + 3814209 = 26150^2 + 1953^2 .

It is a cyclic number.

It is not a de Polignac number, because 687636709 - 2³ = 687636701 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (687636701) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 343818354 + 343818355.

It is an arithmetic number, because the mean of its divisors is an integer number (343818355).

Almost surely, 2^687636709 is an apocalyptic number.

It is an amenable number.

687636709 is a deficient number, since it is larger than the sum of its proper divisors (1).

687636709 is an equidigital number, since it uses as much as digits as its factorization.

687636709 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2286144, while the sum is 52.

The square root of 687636709 is about 26222.8280130119. The cubic root of 687636709 is about 882.6455806077.

The spelling of 687636709 in words is "six hundred eighty-seven million, six hundred thirty-six thousand, seven hundred nine".