1818491821 has 2 divisors, whose sum is σ = 1818491822. Its totient is φ = 1818491820.

The previous prime is 1818491797. The next prime is 1818491839. The reversal of 1818491821 is 1281948181.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1778308900 + 40182921 = 42170^2 + 6339^2 .

It is a cyclic number.

It is not a de Polignac number, because 1818491821 - 2⁷ = 1818491693 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1818491221) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 909245910 + 909245911.

It is an arithmetic number, because the mean of its divisors is an integer number (909245911).

Almost surely, 2^1818491821 is an apocalyptic number.

It is an amenable number.

1818491821 is a deficient number, since it is larger than the sum of its proper divisors (1).

1818491821 is an equidigital number, since it uses as much as digits as its factorization.

1818491821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 36864, while the sum is 43.

The square root of 1818491821 is about 42643.7782214475. The cubic root of 1818491821 is about 1220.5918075178.

The spelling of 1818491821 in words is "one billion, eight hundred eighteen million, four hundred ninety-one thousand, eight hundred twenty-one".