687505128461761 has 9 divisors (see below), whose sum is σ = 700723090579939. Its totient is φ = 674531970128536.

The previous prime is 687505128461737. The next prime is 687505128461771. The reversal of 687505128461761 is 167164821505786.

The square root of 687505128461761 is 26220319.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 495620464626225 + 191884663835536 = 22262535^2 + 13852244^2 .

It is not a de Polignac number, because 687505128461761 - 2²⁵ = 687505094907329 is a prime.

It is a super-2 number, since 2×687505128461761² (a number of 30 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (687505128461731) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 1389429546 + ... + 1389924268.

Almost surely, 2^{687505128461761} is an apocalyptic number.

687505128461761 is the 26220319-th square number.

687505128461761 is the 13110160-th centered octagonal number.

It is an amenable number.

687505128461761 is a deficient number, since it is larger than the sum of its proper divisors (13217962118178).

687505128461761 is an frugal number, since it uses more digits than its factorization.

687505128461761 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 989552 (or 494776 counting only the distinct ones).

The product of its (nonzero) digits is 135475200, while the sum is 67.

The spelling of 687505128461761 in words is "six hundred eighty-seven trillion, five hundred five billion, one hundred twenty-eight million, four hundred sixty-one thousand, seven hundred sixty-one".