687645729 has 9 divisors (see below), whose sum is σ = 993379699. Its totient is φ = 458378040.

The previous prime is 687645671. The next prime is 687645731. The reversal of 687645729 is 927546786.

The square root of 687645729 is 26223.

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

687645729 is a `hidden beast` number, since 6 + 8 + 7 + 64 + 572 + 9 = 666.

It can be written as a sum of positive squares in only one way, i.e., 125955729 + 561690000 = 11223^2 + 23700^2 .

It is a tau number, because it is divible by the number of its divisors (9).

It is not a de Polignac number, because 687645729 - 2¹¹ = 687643681 is a prime.

It is a super-2 number, since 2×687645729² = 945713297223882882, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (687645769) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 74299 + ... + 83039.

Almost surely, 2^687645729 is an apocalyptic number.

687645729 is the 26223-rd square number.

687645729 is the 13112-nd centered octagonal number.

It is an amenable number.

687645729 is a deficient number, since it is larger than the sum of its proper divisors (305733970).

687645729 is an frugal number, since it uses more digits than its factorization.

687645729 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17488 (or 8744 counting only the distinct ones).

The product of its digits is 5080320, while the sum is 54.

The cubic root of 687645729 is about 882.6494399268.

It can be divided in two parts, 6876457 and 29, that added together give a triangular number (6876486 = T₃₇₀₈).

The spelling of 687645729 in words is "six hundred eighty-seven million, six hundred forty-five thousand, seven hundred twenty-nine".