687494981 has 6 divisors (see below), whose sum is σ = 694568082. Its totient is φ = 680427200.

The previous prime is 687494971. The next prime is 687495019. The reversal of 687494981 is 189494786.

It can be written as a sum of positive squares in 3 ways, for example, as 262764100 + 424730881 = 16210^2 + 20609^2 .

It is a de Polignac number, because none of the positive numbers 2^k-687494981 is a prime.

It is a super-2 number, since 2×687494981² = 945298697800380722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (687494911) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 262205 + ... + 264813.

It is an arithmetic number, because the mean of its divisors is an integer number (115761347).

Almost surely, 2^687494981 is an apocalyptic number.

It is an amenable number.

687494981 is a deficient number, since it is larger than the sum of its proper divisors (7073101).

687494981 is an frugal number, since it uses more digits than its factorization.

687494981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5319 (or 2710 counting only the distinct ones).

The product of its digits is 3483648, while the sum is 56.

The square root of 687494981 is about 26220.1254955044. The cubic root of 687494981 is about 882.5849360907.

The spelling of 687494981 in words is "six hundred eighty-seven million, four hundred ninety-four thousand, nine hundred eighty-one".