1809216905 has 4 divisors (see below), whose sum is σ = 2171060292. Its totient is φ = 1447373520.

The previous prime is 1809216863. The next prime is 1809216923. The reversal of 1809216905 is 5096129081.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 865006921 + 944209984 = 29411^2 + 30728^2 .

It is not a de Polignac number, because 1809216905 - 2²⁶ = 1742108041 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 180921686 + ... + 180921695.

It is an arithmetic number, because the mean of its divisors is an integer number (542765073).

Almost surely, 2^1809216905 is an apocalyptic number.

It is an amenable number.

1809216905 is a deficient number, since it is larger than the sum of its proper divisors (361843387).

1809216905 is an equidigital number, since it uses as much as digits as its factorization.

1809216905 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 361843386.

The product of its (nonzero) digits is 38880, while the sum is 41.

The square root of 1809216905 is about 42534.8904430234. The cubic root of 1809216905 is about 1218.5131274738.

The spelling of 1809216905 in words is "one billion, eight hundred nine million, two hundred sixteen thousand, nine hundred five".