687921 has 16 divisors (see below), whose sum is σ = 1021440. Its totient is φ = 408960.

The previous prime is 687917. The next prime is 687923. The reversal of 687921 is 129786.

It is not a de Polignac number, because 687921 - 2² = 687917 is a prime.

It is not an unprimeable number, because it can be changed into a prime (687923) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 925 + ... + 1493.

It is an arithmetic number, because the mean of its divisors is an integer number (63840).

2⁶⁸⁷⁹²¹ is an apocalyptic number.

It is an amenable number.

687921 is a deficient number, since it is larger than the sum of its proper divisors (333519).

687921 is a wasteful number, since it uses less digits than its factorization.

687921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 616.

The product of its digits is 6048, while the sum is 33.

The square root of 687921 is about 829.4100312873. The cubic root of 687921 is about 88.2767201816.

The spelling of 687921 in words is "six hundred eighty-seven thousand, nine hundred twenty-one".