686638987 has 4 divisors (see below), whose sum is σ = 716492880. Its totient is φ = 656785096.

The previous prime is 686638951. The next prime is 686639021. The reversal of 686638987 is 789836686.

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

It is a cyclic number.

It is not a de Polignac number, because 686638987 - 2¹¹ = 686636939 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (686638937) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 14926912 + ... + 14926957.

It is an arithmetic number, because the mean of its divisors is an integer number (179123220).

Almost surely, 2^686638987 is an apocalyptic number.

686638987 is a deficient number, since it is larger than the sum of its proper divisors (29853893).

686638987 is a wasteful number, since it uses less digits than its factorization.

686638987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29853892.

The product of its digits is 20901888, while the sum is 61.

The square root of 686638987 is about 26203.7971866674. The cubic root of 686638987 is about 882.2184843599.

The spelling of 686638987 in words is "six hundred eighty-six million, six hundred thirty-eight thousand, nine hundred eighty-seven".