1645104000821 has 4 divisors (see below), whose sum is σ = 1649247840012. Its totient is φ = 1640960161632.

The previous prime is 1645104000803. The next prime is 1645104000829. The reversal of 1645104000821 is 1280004015461.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1440516046225 + 204587954596 = 1200215^2 + 452314^2 .

It is a cyclic number.

It is not a de Polignac number, because 1645104000821 - 2²⁶ = 1645036891957 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 (1645104000829) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2071919000 + ... + 2071919793.

It is an arithmetic number, because the mean of its divisors is an integer number (412311960003).

Almost surely, 2^{1645104000821} is an apocalyptic number.

It is an amenable number.

1645104000821 is a deficient number, since it is larger than the sum of its proper divisors (4143839191).

1645104000821 is an equidigital number, since it uses as much as digits as its factorization.

1645104000821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4143839190.

The product of its (nonzero) digits is 7680, while the sum is 32.

The spelling of 1645104000821 in words is "one trillion, six hundred forty-five billion, one hundred four million, eight hundred twenty-one", and thus it is an aban number.