1809680861 has 2 divisors, whose sum is σ = 1809680862. Its totient is φ = 1809680860.

The previous prime is 1809680797. The next prime is 1809680869. The reversal of 1809680861 is 1680869081.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1805400100 + 4280761 = 42490^2 + 2069^2 .

It is an emirp because it is prime and its reverse (1680869081) is a distict prime. It is also a bemirp because it and its reverse can be mirrored producing other two distinct primes, 1980896081 and 1806980891.

It is a cyclic number.

It is not a de Polignac number, because 1809680861 - 2⁶ = 1809680797 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1809680869) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 904840430 + 904840431.

It is an arithmetic number, because the mean of its divisors is an integer number (904840431).

Almost surely, 2^1809680861 is an apocalyptic number.

It is an amenable number.

1809680861 is a deficient number, since it is larger than the sum of its proper divisors (1).

1809680861 is an equidigital number, since it uses as much as digits as its factorization.

1809680861 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 165888, while the sum is 47.

The square root of 1809680861 is about 42540.3439219760. The cubic root of 1809680861 is about 1218.6172771673.

The spelling of 1809680861 in words is "one billion, eight hundred nine million, six hundred eighty thousand, eight hundred sixty-one".