1686755921 has 2 divisors, whose sum is σ = 1686755922. Its totient is φ = 1686755920.

The previous prime is 1686755891. The next prime is 1686755923. The reversal of 1686755921 is 1295576861.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1659340225 + 27415696 = 40735^2 + 5236^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1686755921 is a prime.

Together with 1686755923, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1686755921.

It is not a weakly prime, because it can be changed into another prime (1686755923) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 843377960 + 843377961.

It is an arithmetic number, because the mean of its divisors is an integer number (843377961).

Almost surely, 2^1686755921 is an apocalyptic number.

It is an amenable number.

1686755921 is a deficient number, since it is larger than the sum of its proper divisors (1).

1686755921 is an equidigital number, since it uses as much as digits as its factorization.

1686755921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 907200, while the sum is 50.

The square root of 1686755921 is about 41070.1341731434. The cubic root of 1686755921 is about 1190.3757778008.

The spelling of 1686755921 in words is "one billion, six hundred eighty-six million, seven hundred fifty-five thousand, nine hundred twenty-one".