1813720861 has 2 divisors, whose sum is σ = 1813720862. Its totient is φ = 1813720860.

The previous prime is 1813720859. The next prime is 1813720903. The reversal of 1813720861 is 1680273181.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1095212836 + 718508025 = 33094^2 + 26805^2 .

It is an emirp because it is prime and its reverse (1680273181) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1813720861 - 2¹ = 1813720859 is a prime.

Together with 1813720859, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 1813720861.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1813720061) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 906860430 + 906860431.

It is an arithmetic number, because the mean of its divisors is an integer number (906860431).

Almost surely, 2^1813720861 is an apocalyptic number.

It is an amenable number.

1813720861 is a deficient number, since it is larger than the sum of its proper divisors (1).

1813720861 is an equidigital number, since it uses as much as digits as its factorization.

1813720861 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 16128, while the sum is 37.

The square root of 1813720861 is about 42587.8017864271. The cubic root of 1813720861 is about 1219.5234322899.

The spelling of 1813720861 in words is "one billion, eight hundred thirteen million, seven hundred twenty thousand, eight hundred sixty-one".