1821538445 has 4 divisors (see below), whose sum is σ = 2185846140. Its totient is φ = 1457230752.

The previous prime is 1821538421. The next prime is 1821538451. The reversal of 1821538445 is 5448351281.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 5448351281 = 5519 ⋅987199.

It can be written as a sum of positive squares in 2 ways, for example, as 342213001 + 1479325444 = 18499^2 + 38462^2 .

It is a cyclic number.

It is not a de Polignac number, because 1821538445 - 2²⁴ = 1804761229 is a prime.

It is a super-2 number, since 2×1821538445² = 6636004613226036050, which contains 22 as substring.

It is a congruent 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, 182153840 + ... + 182153849.

It is an arithmetic number, because the mean of its divisors is an integer number (546461535).

Almost surely, 2^1821538445 is an apocalyptic number.

It is an amenable number.

1821538445 is a deficient number, since it is larger than the sum of its proper divisors (364307695).

1821538445 is an equidigital number, since it uses as much as digits as its factorization.

1821538445 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 364307694.

The product of its digits is 153600, while the sum is 41.

The square root of 1821538445 is about 42679.4850601551. The cubic root of 1821538445 is about 1221.2730697730.

The spelling of 1821538445 in words is "one billion, eight hundred twenty-one million, five hundred thirty-eight thousand, four hundred forty-five".