1812820997 has 16 divisors (see below), whose sum is σ = 1987091568. Its totient is φ = 1643604480.

The previous prime is 1812820991. The next prime is 1812821009. The reversal of 1812820997 is 7990282181.

It can be written as a sum of positive squares in 8 ways, for example, as 41589601 + 1771231396 = 6449^2 + 42086^2 .

It is a cyclic number.

It is not a de Polignac number, because 1812820997 - 2⁴ = 1812820981 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 (1812820991) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 818063 + ... + 820275.

It is an arithmetic number, because the mean of its divisors is an integer number (124193223).

Almost surely, 2^1812820997 is an apocalyptic number.

It is an amenable number.

1812820997 is a deficient number, since it is larger than the sum of its proper divisors (174270571).

1812820997 is a wasteful number, since it uses less digits than its factorization.

1812820997 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3320.

The product of its (nonzero) digits is 145152, while the sum is 47.

The square root of 1812820997 is about 42577.2356664920. The cubic root of 1812820997 is about 1219.3217131247.

The spelling of 1812820997 in words is "one billion, eight hundred twelve million, eight hundred twenty thousand, nine hundred ninety-seven".