1681116221 has 2 divisors, whose sum is σ = 1681116222. Its totient is φ = 1681116220.

The previous prime is 1681116187. The next prime is 1681116259. The reversal of 1681116221 is 1226111861.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1286656900 + 394459321 = 35870^2 + 19861^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1681116221 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1681116121) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 840558110 + 840558111.

It is an arithmetic number, because the mean of its divisors is an integer number (840558111).

Almost surely, 2^1681116221 is an apocalyptic number.

It is an amenable number.

1681116221 is a deficient number, since it is larger than the sum of its proper divisors (1).

1681116221 is an equidigital number, since it uses as much as digits as its factorization.

1681116221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1152, while the sum is 29.

The square root of 1681116221 is about 41001.4173047713. The cubic root of 1681116221 is about 1189.0476152208.

The spelling of 1681116221 in words is "one billion, six hundred eighty-one million, one hundred sixteen thousand, two hundred twenty-one".