1816818021 has 6 divisors (see below), whose sum is σ = 2624292710. Its totient is φ = 1211212008.

The previous prime is 1816817971. The next prime is 1816818037. The reversal of 1816818021 is 1208186181.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 1465817796 + 351000225 = 38286^2 + 18735^2 .

It is not a de Polignac number, because 1816818021 - 2²⁵ = 1783263589 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1816818121) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 100934326 + ... + 100934343.

Almost surely, 2^1816818021 is an apocalyptic number.

It is an amenable number.

1816818021 is a deficient number, since it is larger than the sum of its proper divisors (807474689).

1816818021 is a wasteful number, since it uses less digits than its factorization.

1816818021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 201868675 (or 201868672 counting only the distinct ones).

The product of its (nonzero) digits is 6144, while the sum is 36.

The square root of 1816818021 is about 42624.1483316676. The cubic root of 1816818021 is about 1220.2172015416.

The spelling of 1816818021 in words is "one billion, eight hundred sixteen million, eight hundred eighteen thousand, twenty-one".