687821521 has 8 divisors (see below), whose sum is σ = 710329088. Its totient is φ = 665334000.

The previous prime is 687821483. The next prime is 687821551. The reversal of 687821521 is 125128786.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 687821521 - 2¹⁵ = 687788753 is a prime.

It is not an unprimeable number, because it can be changed into a prime (687821551) 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 7 ways as a sum of consecutive naturals, for example, 99931 + ... + 106591.

It is an arithmetic number, because the mean of its divisors is an integer number (88791136).

Almost surely, 2^687821521 is an apocalyptic number.

It is an amenable number.

687821521 is a deficient number, since it is larger than the sum of its proper divisors (22507567).

687821521 is a wasteful number, since it uses less digits than its factorization.

687821521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10023.

The product of its digits is 53760, while the sum is 40.

The square root of 687821521 is about 26226.3516524888. The cubic root of 687821521 is about 882.7246479802.

The spelling of 687821521 in words is "six hundred eighty-seven million, eight hundred twenty-one thousand, five hundred twenty-one".