687987977 has 4 divisors (see below), whose sum is σ = 728457876. Its totient is φ = 647518080.

The previous prime is 687987907. The next prime is 687987997. The reversal of 687987977 is 779789786.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 779789786 = 2 ⋅389894893.

It can be written as a sum of positive squares in 2 ways, for example, as 207676921 + 480311056 = 14411^2 + 21916^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-687987977 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (687987907) 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, 20234924 + ... + 20234957.

It is an arithmetic number, because the mean of its divisors is an integer number (182114469).

Almost surely, 2^687987977 is an apocalyptic number.

It is an amenable number.

687987977 is a deficient number, since it is larger than the sum of its proper divisors (40469899).

687987977 is a wasteful number, since it uses less digits than its factorization.

687987977 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40469898.

The product of its digits is 74680704, while the sum is 68.

The square root of 687987977 is about 26229.5249099178. The cubic root of 687987977 is about 882.7958500571.

The spelling of 687987977 in words is "six hundred eighty-seven million, nine hundred eighty-seven thousand, nine hundred seventy-seven".