1643641 has 2 divisors, whose sum is σ = 1643642. Its totient is φ = 1643640.

The previous prime is 1643639. The next prime is 1643659. The reversal of 1643641 is 1463461.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1010025 + 633616 = 1005^2 + 796^2 .

It is a cyclic number.

It is not a de Polignac number, because 1643641 - 2¹ = 1643639 is a prime.

Together with 1643639, it forms a pair of twin primes.

1643641 is a lucky number.

It is equal to p₁₂₄₁₈₉ and since 1643641 and 124189 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (1643141) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 821820 + 821821.

It is an arithmetic number, because the mean of its divisors is an integer number (821821).

2^1643641 is an apocalyptic number.

It is an amenable number.

1643641 is a deficient number, since it is larger than the sum of its proper divisors (1).

1643641 is an equidigital number, since it uses as much as digits as its factorization.

1643641 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1728, while the sum is 25.

The square root of 1643641 is about 1282.0456310132. The cubic root of 1643641 is about 118.0145773430.

The spelling of 1643641 in words is "one million, six hundred forty-three thousand, six hundred forty-one".