1781549849 has 2 divisors, whose sum is σ = 1781549850. Its totient is φ = 1781549848.

The previous prime is 1781549831. The next prime is 1781549851. The reversal of 1781549849 is 9489451871.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1760389849 + 21160000 = 41957^2 + 4600^2 .

It is an emirp because it is prime and its reverse (9489451871) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1781549849 is a prime.

Together with 1781549851, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 1781549794 and 1781549803.

It is not a weakly prime, because it can be changed into another prime (1781549449) 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, 890774924 + 890774925.

It is an arithmetic number, because the mean of its divisors is an integer number (890774925).

Almost surely, 2^1781549849 is an apocalyptic number.

It is an amenable number.

1781549849 is a deficient number, since it is larger than the sum of its proper divisors (1).

1781549849 is an equidigital number, since it uses as much as digits as its factorization.

1781549849 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2903040, while the sum is 56.

The square root of 1781549849 is about 42208.4096952254. The cubic root of 1781549849 is about 1212.2699118299.

The spelling of 1781549849 in words is "one billion, seven hundred eighty-one million, five hundred forty-nine thousand, eight hundred forty-nine".