1645561 has 2 divisors, whose sum is σ = 1645562. Its totient is φ = 1645560.

The previous prime is 1645559. The next prime is 1645601. The reversal of 1645561 is 1655461.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1092025 + 553536 = 1045^2 + 744^2 .

It is an emirp because it is prime and its reverse (1655461) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1645561 - 2¹ = 1645559 is a prime.

Together with 1645559, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (1645661) 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 as a sum of consecutive naturals, namely, 822780 + 822781.

It is an arithmetic number, because the mean of its divisors is an integer number (822781).

2^1645561 is an apocalyptic number.

It is an amenable number.

1645561 is a deficient number, since it is larger than the sum of its proper divisors (1).

1645561 is an equidigital number, since it uses as much as digits as its factorization.

1645561 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3600, while the sum is 28.

The square root of 1645561 is about 1282.7942157649. The cubic root of 1645561 is about 118.0605119108.

The spelling of 1645561 in words is "one million, six hundred forty-five thousand, five hundred sixty-one".