1685187221 has 2 divisors, whose sum is σ = 1685187222. Its totient is φ = 1685187220.

The previous prime is 1685187181. The next prime is 1685187239. The reversal of 1685187221 is 1227815861.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1526074225 + 159112996 = 39065^2 + 12614^2 .

It is a cyclic number.

It is not a de Polignac number, because 1685187221 - 2¹⁰ = 1685186197 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1685187241) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 842593610 + 842593611.

It is an arithmetic number, because the mean of its divisors is an integer number (842593611).

Almost surely, 2^1685187221 is an apocalyptic number.

It is an amenable number.

1685187221 is a deficient number, since it is larger than the sum of its proper divisors (1).

1685187221 is an equidigital number, since it uses as much as digits as its factorization.

1685187221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 53760, while the sum is 41.

The square root of 1685187221 is about 41051.0319115123. The cubic root of 1685187221 is about 1190.0066428554.

The spelling of 1685187221 in words is "one billion, six hundred eighty-five million, one hundred eighty-seven thousand, two hundred twenty-one".