686986981 has 2 divisors, whose sum is σ = 686986982. Its totient is φ = 686986980.

The previous prime is 686986967. The next prime is 686986991. The reversal of 686986981 is 189689686.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 587286756 + 99700225 = 24234^2 + 9985^2 .

It is a cyclic number.

It is not a de Polignac number, because 686986981 - 2¹¹ = 686984933 is a prime.

It is a super-2 number, since 2×686986981² = 943902224126988722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (686986961) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 343493490 + 343493491.

It is an arithmetic number, because the mean of its divisors is an integer number (343493491).

Almost surely, 2^686986981 is an apocalyptic number.

It is an amenable number.

686986981 is a deficient number, since it is larger than the sum of its proper divisors (1).

686986981 is an equidigital number, since it uses as much as digits as its factorization.

686986981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 8957952, while the sum is 61.

The square root of 686986981 is about 26210.4364900701. The cubic root of 686986981 is about 882.3674975945.

The spelling of 686986981 in words is "six hundred eighty-six million, nine hundred eighty-six thousand, nine hundred eighty-one".