1781664541 has 4 divisors (see below), whose sum is σ = 1782368800. Its totient is φ = 1780960284.

The previous prime is 1781664527. The next prime is 1781664551. The reversal of 1781664541 is 1454661871.

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: 1454661871 = 13 ⋅111897067.

It is a cyclic number.

It is not a de Polignac number, because 1781664541 - 2⁵ = 1781664509 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1781664551) 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, 348321 + ... + 353398.

It is an arithmetic number, because the mean of its divisors is an integer number (445592200).

Almost surely, 2^1781664541 is an apocalyptic number.

It is an amenable number.

1781664541 is a deficient number, since it is larger than the sum of its proper divisors (704259).

1781664541 is an equidigital number, since it uses as much as digits as its factorization.

1781664541 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 704258.

The product of its digits is 161280, while the sum is 43.

The square root of 1781664541 is about 42209.7683125601. The cubic root of 1781664541 is about 1212.2959256360.

The spelling of 1781664541 in words is "one billion, seven hundred eighty-one million, six hundred sixty-four thousand, five hundred forty-one".