1581643 has 4 divisors (see below), whose sum is σ = 1807600. Its totient is φ = 1355688.

The previous prime is 1581637. The next prime is 1581649. The reversal of 1581643 is 3461851.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 3461851 = 463 ⋅7477.

It is an interprime number because it is at equal distance from previous prime (1581637) and next prime (1581649).

It is a cyclic number.

It is not a de Polignac number, because 1581643 - 2⁵ = 1581611 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1581649) 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, 112968 + ... + 112981.

It is an arithmetic number, because the mean of its divisors is an integer number (451900).

2^1581643 is an apocalyptic number.

1581643 is a deficient number, since it is larger than the sum of its proper divisors (225957).

1581643 is an equidigital number, since it uses as much as digits as its factorization.

1581643 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 225956.

The product of its digits is 2880, while the sum is 28.

The square root of 1581643 is about 1257.6338894925. The cubic root of 1581643 is about 116.5116862782.

The spelling of 1581643 in words is "one million, five hundred eighty-one thousand, six hundred forty-three".