1641782561 has 4 divisors (see below), whose sum is σ = 1641921792. Its totient is φ = 1641643332.

The previous prime is 1641782509. The next prime is 1641782567. The reversal of 1641782561 is 1652871461.

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: 1652871461 = 17 ⋅97227733.

It is a cyclic number.

It is not a de Polignac number, because 1641782561 - 2¹⁸ = 1641520417 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1641782567) 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, 50105 + ... + 76118.

It is an arithmetic number, because the mean of its divisors is an integer number (410480448).

Almost surely, 2^1641782561 is an apocalyptic number.

It is an amenable number.

1641782561 is a deficient number, since it is larger than the sum of its proper divisors (139231).

1641782561 is a wasteful number, since it uses less digits than its factorization.

1641782561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 139230.

The product of its digits is 80640, while the sum is 41.

The square root of 1641782561 is about 40518.9160886616. The cubic root of 1641782561 is about 1179.7008149371.

Subtracting 1641782561 from its reverse (1652871461), we obtain a square (11088900 = 3330²).

The spelling of 1641782561 in words is "one billion, six hundred forty-one million, seven hundred eighty-two thousand, five hundred sixty-one".