1645821161 has 8 divisors (see below), whose sum is σ = 1692373320. Its totient is φ = 1599378048.

The previous prime is 1645821127. The next prime is 1645821179. The reversal of 1645821161 is 1611285461.

It can be written as a sum of positive squares in 4 ways, for example, as 836077225 + 809743936 = 28915^2 + 28456^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1645821161 - 2¹⁸ = 1645559017 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1645823161) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3845 + ... + 57501.

It is an arithmetic number, because the mean of its divisors is an integer number (211546665).

Almost surely, 2^1645821161 is an apocalyptic number.

It is an amenable number.

1645821161 is a deficient number, since it is larger than the sum of its proper divisors (46552159).

1645821161 is an equidigital number, since it uses as much as digits as its factorization.

1645821161 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 54523.

The product of its digits is 11520, while the sum is 35.

The square root of 1645821161 is about 40568.7214612440. The cubic root of 1645821161 is about 1180.6673331949.

The spelling of 1645821161 in words is "one billion, six hundred forty-five million, eight hundred twenty-one thousand, one hundred sixty-one".