1211780681 has 2 divisors, whose sum is σ = 1211780682. Its totient is φ = 1211780680.

The previous prime is 1211780629. The next prime is 1211780741. The reversal of 1211780681 is 1860871121.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1050084025 + 161696656 = 32405^2 + 12716^2 .

It is an emirp because it is prime and its reverse (1860871121) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1211780681 - 2⁶ = 1211780617 is a prime.

It is a super-2 number, since 2×1211780681² = 2936824837689647522, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (1211780611) 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, 605890340 + 605890341.

It is an arithmetic number, because the mean of its divisors is an integer number (605890341).

Almost surely, 2^1211780681 is an apocalyptic number.

It is an amenable number.

1211780681 is a deficient number, since it is larger than the sum of its proper divisors (1).

1211780681 is an equidigital number, since it uses as much as digits as its factorization.

1211780681 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 5376, while the sum is 35.

The square root of 1211780681 is about 34810.6403417116. The cubic root of 1211780681 is about 1066.1247071819.

The spelling of 1211780681 in words is "one billion, two hundred eleven million, seven hundred eighty thousand, six hundred eighty-one".