687909785 has 4 divisors (see below), whose sum is σ = 825491748. Its totient is φ = 550327824.

The previous prime is 687909769. The next prime is 687909793. The reversal of 687909785 is 587909786.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 483076441 + 204833344 = 21979^2 + 14312^2 .

It is a cyclic number.

It is not a de Polignac number, because 687909785 - 2⁴ = 687909769 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 68790974 + ... + 68790983.

It is an arithmetic number, because the mean of its divisors is an integer number (206372937).

Almost surely, 2^687909785 is an apocalyptic number.

It is an amenable number.

687909785 is a deficient number, since it is larger than the sum of its proper divisors (137581963).

687909785 is a wasteful number, since it uses less digits than its factorization.

687909785 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 137581962.

The product of its (nonzero) digits is 7620480, while the sum is 59.

The square root of 687909785 is about 26228.0343335142. The cubic root of 687909785 is about 882.7624046140.

Subtracting from 687909785 its reverse (587909786), we obtain a palindrome (99999999).

The spelling of 687909785 in words is "six hundred eighty-seven million, nine hundred nine thousand, seven hundred eighty-five".