1781661617 has 2 divisors, whose sum is σ = 1781661618. Its totient is φ = 1781661616.

The previous prime is 1781661599. The next prime is 1781661653. The reversal of 1781661617 is 7161661871.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1270494736 + 511166881 = 35644^2 + 22609^2 .

It is a cyclic number.

It is not a de Polignac number, because 1781661617 - 2¹⁴ = 1781645233 is a prime.

It is not a weakly prime, because it can be changed into another prime (1781661017) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 890830808 + 890830809.

It is an arithmetic number, because the mean of its divisors is an integer number (890830809).

Almost surely, 2^1781661617 is an apocalyptic number.

It is an amenable number.

1781661617 is a deficient number, since it is larger than the sum of its proper divisors (1).

1781661617 is an equidigital number, since it uses as much as digits as its factorization.

1781661617 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 84672, while the sum is 44.

The square root of 1781661617 is about 42209.7336760136. The cubic root of 1781661617 is about 1212.2952624443.

The spelling of 1781661617 in words is "one billion, seven hundred eighty-one million, six hundred sixty-one thousand, six hundred seventeen".