687551806821 has 32 divisors (see below), whose sum is σ = 1004862583296. Its totient is φ = 414707832000.

The previous prime is 687551806817. The next prime is 687551806849. The reversal of 687551806821 is 128608155786.

687551806821 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 687551806821 - 2² = 687551806817 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (687551806421) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 6181915 + ... + 6292151.

It is an arithmetic number, because the mean of its divisors is an integer number (31401955728).

Almost surely, 2^687551806821 is an apocalyptic number.

It is an amenable number.

687551806821 is a deficient number, since it is larger than the sum of its proper divisors (317310776475).

687551806821 is a wasteful number, since it uses less digits than its factorization.

687551806821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 111153.

The product of its (nonzero) digits is 6451200, while the sum is 57.

The spelling of 687551806821 in words is "six hundred eighty-seven billion, five hundred fifty-one million, eight hundred six thousand, eight hundred twenty-one".