687981 has 12 divisors (see below), whose sum is σ = 1054176. Its totient is φ = 390960.

The previous prime is 687977. The next prime is 688003. The reversal of 687981 is 189786.

It is not a de Polignac number, because 687981 - 2² = 687977 is a prime.

It is a super-2 number, since 2×687981² = 946635712722, which contains 22 as substring.

687981 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (687901) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 3711 + ... + 3891.

It is an arithmetic number, because the mean of its divisors is an integer number (87848).

2⁶⁸⁷⁹⁸¹ is an apocalyptic number.

It is an amenable number.

687981 is a deficient number, since it is larger than the sum of its proper divisors (366195).

687981 is an equidigital number, since it uses as much as digits as its factorization.

687981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 372 (or 191 counting only the distinct ones).

The product of its digits is 24192, while the sum is 39.

The square root of 687981 is about 829.4462007870. The cubic root of 687981 is about 88.2792865854.

The spelling of 687981 in words is "six hundred eighty-seven thousand, nine hundred eighty-one".