686755981 has 4 divisors (see below), whose sum is σ = 687410464. Its totient is φ = 686101500.

The previous prime is 686755973. The next prime is 686755997. The reversal of 686755981 is 189557686.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 686755981 - 2³ = 686755973 is a prime.

It is a super-2 number, since 2×686755981² = 943267554878544722, 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 (686755081) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 325665 + ... + 327766.

It is an arithmetic number, because the mean of its divisors is an integer number (171852616).

Almost surely, 2^686755981 is an apocalyptic number.

It is an amenable number.

686755981 is a deficient number, since it is larger than the sum of its proper divisors (654483).

686755981 is a wasteful number, since it uses less digits than its factorization.

686755981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 654482.

The product of its digits is 3628800, while the sum is 55.

The square root of 686755981 is about 26206.0294779656. The cubic root of 686755981 is about 882.2685875484.

The spelling of 686755981 in words is "six hundred eighty-six million, seven hundred fifty-five thousand, nine hundred eighty-one".