281720161 has 2 divisors, whose sum is σ = 281720162. Its totient is φ = 281720160.

The previous prime is 281720147. The next prime is 281720167. The reversal of 281720161 is 161027182.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 231040000 + 50680161 = 15200^2 + 7119^2 .

It is a cyclic number.

It is not a de Polignac number, because 281720161 - 2⁹ = 281719649 is a prime.

It is a super-2 number, since 2×281720161² = 158732498227731842, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (281720167) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 140860080 + 140860081.

It is an arithmetic number, because the mean of its divisors is an integer number (140860081).

Almost surely, 2^281720161 is an apocalyptic number.

It is an amenable number.

281720161 is a deficient number, since it is larger than the sum of its proper divisors (1).

281720161 is an equidigital number, since it uses as much as digits as its factorization.

281720161 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1344, while the sum is 28.

The square root of 281720161 is about 16784.5214706884. The cubic root of 281720161 is about 655.5502328284.

The spelling of 281720161 in words is "two hundred eighty-one million, seven hundred twenty thousand, one hundred sixty-one".