1809669661 has 2 divisors, whose sum is σ = 1809669662. Its totient is φ = 1809669660.

The previous prime is 1809669607. The next prime is 1809669677. The reversal of 1809669661 is 1669669081.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1624573636 + 185096025 = 40306^2 + 13605^2 .

It is an emirp because it is prime and its reverse (1669669081) is a distict prime. It is also a bemirp because it and its reverse can be mirrored producing other two distinct primes, 1996996081 and 1806996991.

It is a cyclic number.

It is not a de Polignac number, because 1809669661 - 2²⁹ = 1272798749 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 1809669599 and 1809669608.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1809669461) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 904834830 + 904834831.

It is an arithmetic number, because the mean of its divisors is an integer number (904834831).

Almost surely, 2^1809669661 is an apocalyptic number.

It is an amenable number.

1809669661 is a deficient number, since it is larger than the sum of its proper divisors (1).

1809669661 is an equidigital number, since it uses as much as digits as its factorization.

1809669661 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 839808, while the sum is 52.

The square root of 1809669661 is about 42540.2122820279. The cubic root of 1809669661 is about 1218.6147631805.

The spelling of 1809669661 in words is "one billion, eight hundred nine million, six hundred sixty-nine thousand, six hundred sixty-one".