687565981 has 2 divisors, whose sum is σ = 687565982. Its totient is φ = 687565980.

The previous prime is 687565951. The next prime is 687565997. The reversal of 687565981 is 189565786.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 684084025 + 3481956 = 26155^2 + 1866^2 .

It is a cyclic number.

It is not a de Polignac number, because 687565981 - 2¹⁵ = 687533213 is a prime.

It is a super-2 number, since 2×687565981² = 945493956456984722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (687565951) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 343782990 + 343782991.

It is an arithmetic number, because the mean of its divisors is an integer number (343782991).

Almost surely, 2^687565981 is an apocalyptic number.

It is an amenable number.

687565981 is a deficient number, since it is larger than the sum of its proper divisors (1).

687565981 is an equidigital number, since it uses as much as digits as its factorization.

687565981 is an evil number, because the sum of its binary digits is even.

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

The square root of 687565981 is about 26221.4793823690. The cubic root of 687565981 is about 882.6153175845.

The spelling of 687565981 in words is "six hundred eighty-seven million, five hundred sixty-five thousand, nine hundred eighty-one".