1811621781097 has 2 divisors, whose sum is σ = 1811621781098. Its totient is φ = 1811621781096.

The previous prime is 1811621781061. The next prime is 1811621781107. The reversal of 1811621781097 is 7901871261181.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1520414768601 + 291207012496 = 1233051^2 + 539636^2 .

It is a cyclic number.

It is not a de Polignac number, because 1811621781097 - 2¹¹ = 1811621779049 is a prime.

It is not a weakly prime, because it can be changed into another prime (1811621781037) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 905810890548 + 905810890549.

It is an arithmetic number, because the mean of its divisors is an integer number (905810890549).

Almost surely, 2^{1811621781097} is an apocalyptic number.

It is an amenable number.

1811621781097 is a deficient number, since it is larger than the sum of its proper divisors (1).

1811621781097 is an equidigital number, since it uses as much as digits as its factorization.

1811621781097 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 338688, while the sum is 52.

The spelling of 1811621781097 in words is "one trillion, eight hundred eleven billion, six hundred twenty-one million, seven hundred eighty-one thousand, ninety-seven".