1681585921 has 4 divisors (see below), whose sum is σ = 1681758144. Its totient is φ = 1681413700.

The previous prime is 1681585903. The next prime is 1681585933. The reversal of 1681585921 is 1295851861.

It is a happy number.

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: 1295851861 = 22777 ⋅56893.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1681585921 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1681585951) 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, 70525 + ... + 91306.

It is an arithmetic number, because the mean of its divisors is an integer number (420439536).

Almost surely, 2^1681585921 is an apocalyptic number.

It is an amenable number.

1681585921 is a deficient number, since it is larger than the sum of its proper divisors (172223).

1681585921 is a wasteful number, since it uses less digits than its factorization.

1681585921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 172222.

The product of its digits is 172800, while the sum is 46.

The square root of 1681585921 is about 41007.1447555179. The cubic root of 1681585921 is about 1189.1583439640.

The spelling of 1681585921 in words is "one billion, six hundred eighty-one million, five hundred eighty-five thousand, nine hundred twenty-one".