686611701821 has 2 divisors, whose sum is σ = 686611701822. Its totient is φ = 686611701820.

The previous prime is 686611701817. The next prime is 686611701859. The reversal of 686611701821 is 128107116686.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 574427568100 + 112184133721 = 757910^2 + 334939^2 .

It is a cyclic number.

It is not a de Polignac number, because 686611701821 - 2² = 686611701817 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (686611700821) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 343305850910 + 343305850911.

It is an arithmetic number, because the mean of its divisors is an integer number (343305850911).

Almost surely, 2^686611701821 is an apocalyptic number.

It is an amenable number.

686611701821 is a deficient number, since it is larger than the sum of its proper divisors (1).

686611701821 is an equidigital number, since it uses as much as digits as its factorization.

686611701821 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 193536, while the sum is 47.

The spelling of 686611701821 in words is "six hundred eighty-six billion, six hundred eleven million, seven hundred one thousand, eight hundred twenty-one".