1681952221 has 2 divisors, whose sum is σ = 1681952222. Its totient is φ = 1681952220.

The previous prime is 1681952203. The next prime is 1681952227. The reversal of 1681952221 is 1222591861.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1395022500 + 286929721 = 37350^2 + 16939^2 .

It is a cyclic number.

It is not a de Polignac number, because 1681952221 - 2⁵ = 1681952189 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1681952227) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 840976110 + 840976111.

It is an arithmetic number, because the mean of its divisors is an integer number (840976111).

Almost surely, 2^1681952221 is an apocalyptic number.

It is an amenable number.

1681952221 is a deficient number, since it is larger than the sum of its proper divisors (1).

1681952221 is an equidigital number, since it uses as much as digits as its factorization.

1681952221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 17280, while the sum is 37.

The square root of 1681952221 is about 41011.6108071848. The cubic root of 1681952221 is about 1189.2446825153.

The spelling of 1681952221 in words is "one billion, six hundred eighty-one million, nine hundred fifty-two thousand, two hundred twenty-one".