1818156661 has 2 divisors, whose sum is σ = 1818156662. Its totient is φ = 1818156660.

The previous prime is 1818156643. The next prime is 1818156671. The reversal of 1818156661 is 1666518181.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1492354161 + 325802500 = 38631^2 + 18050^2 .

It is a cyclic number.

It is not a de Polignac number, because 1818156661 - 2⁵ = 1818156629 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1818156611) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 909078330 + 909078331.

It is an arithmetic number, because the mean of its divisors is an integer number (909078331).

Almost surely, 2^1818156661 is an apocalyptic number.

It is an amenable number.

1818156661 is a deficient number, since it is larger than the sum of its proper divisors (1).

1818156661 is an equidigital number, since it uses as much as digits as its factorization.

1818156661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 69120, while the sum is 43.

The square root of 1818156661 is about 42639.8482759965. The cubic root of 1818156661 is about 1220.5168152117.

The spelling of 1818156661 in words is "one billion, eight hundred eighteen million, one hundred fifty-six thousand, six hundred sixty-one".