687908023921 has 4 divisors (see below), whose sum is σ = 687909968100. Its totient is φ = 687906079744.

The previous prime is 687908023919. The next prime is 687908023951. The reversal of 687908023921 is 129320809786.

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 109032040000 + 578875983921 = 330200^2 + 760839^2 .

It is a cyclic number.

It is not a de Polignac number, because 687908023921 - 2¹ = 687908023919 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (687908023951) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 274456 + ... + 1204633.

It is an arithmetic number, because the mean of its divisors is an integer number (171977492025).

Almost surely, 2^687908023921 is an apocalyptic number.

It is an amenable number.

687908023921 is a deficient number, since it is larger than the sum of its proper divisors (1944179).

687908023921 is a wasteful number, since it uses less digits than its factorization.

687908023921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1944178.

The product of its (nonzero) digits is 2612736, while the sum is 55.

The spelling of 687908023921 in words is "six hundred eighty-seven billion, nine hundred eight million, twenty-three thousand, nine hundred twenty-one".