1643530561 has 4 divisors (see below), whose sum is σ = 1644116400. Its totient is φ = 1642944724.

The previous prime is 1643530529. The next prime is 1643530591. The reversal of 1643530561 is 1650353461.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 1650353461 = 2237 ⋅737753.

It is a cyclic number.

It is not a de Polignac number, because 1643530561 - 2⁵ = 1643530529 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1643530591) 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, 288691 + ... + 294328.

It is an arithmetic number, because the mean of its divisors is an integer number (411029100).

Almost surely, 2^1643530561 is an apocalyptic number.

It is an amenable number.

1643530561 is a deficient number, since it is larger than the sum of its proper divisors (585839).

1643530561 is an equidigital number, since it uses as much as digits as its factorization.

1643530561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 585838.

The product of its (nonzero) digits is 32400, while the sum is 34.

The square root of 1643530561 is about 40540.4805225592. The cubic root of 1643530561 is about 1180.1193408457.

The spelling of 1643530561 in words is "one billion, six hundred forty-three million, five hundred thirty thousand, five hundred sixty-one".