1641821805 has 80 divisors (see below), whose sum is σ = 3279109680. Its totient is φ = 780337152.

The previous prime is 1641821789. The next prime is 1641821809. The reversal of 1641821805 is 5081281461.

1641821805 is a `hidden beast` number, since 1 + 641 + 8 + 2 + 1 + 8 + 0 + 5 = 666.

It can be written as a sum of positive squares in 8 ways, for example, as 842724 + 1640979081 = 918^2 + 40509^2 .

It is not a de Polignac number, because 1641821805 - 2⁴ = 1641821789 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1641821805.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1641821809) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 147309 + ... + 158061.

It is an arithmetic number, because the mean of its divisors is an integer number (40988871).

Almost surely, 2^1641821805 is an apocalyptic number.

1641821805 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

1641821805 is a deficient number, since it is larger than the sum of its proper divisors (1637287875).

1641821805 is a wasteful number, since it uses less digits than its factorization.

1641821805 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10812 (or 10803 counting only the distinct ones).

The product of its (nonzero) digits is 15360, while the sum is 36.

The square root of 1641821805 is about 40519.4003534110. The cubic root of 1641821805 is about 1179.7102144380.

The spelling of 1641821805 in words is "one billion, six hundred forty-one million, eight hundred twenty-one thousand, eight hundred five".