281391661 has 2 divisors, whose sum is σ = 281391662. Its totient is φ = 281391660.

The previous prime is 281391659. The next prime is 281391689. The reversal of 281391661 is 166193182.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 227074761 + 54316900 = 15069^2 + 7370^2 .

It is a cyclic number.

It is not a de Polignac number, because 281391661 - 2¹ = 281391659 is a prime.

Together with 281391659, it forms a pair of twin primes.

It is equal to p_15297670 and since 281391661 and 15297670 have the same sum of digits, it is a Honaker prime.

It is a self number, because there is not a number n which added to its sum of digits gives 281391661.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (281391161) 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, 140695830 + 140695831.

It is an arithmetic number, because the mean of its divisors is an integer number (140695831).

Almost surely, 2^281391661 is an apocalyptic number.

It is an amenable number.

281391661 is a deficient number, since it is larger than the sum of its proper divisors (1).

281391661 is an equidigital number, since it uses as much as digits as its factorization.

281391661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 15552, while the sum is 37.

The square root of 281391661 is about 16774.7328145637. The cubic root of 281391661 is about 655.2953321173.

The spelling of 281391661 in words is "two hundred eighty-one million, three hundred ninety-one thousand, six hundred sixty-one".