1680591921 has 4 divisors (see below), whose sum is σ = 2240789232. Its totient is φ = 1120394612.

The previous prime is 1680591901. The next prime is 1680591923. The reversal of 1680591921 is 1291950861.

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.

It is a cyclic number.

It is not a de Polignac number, because 1680591921 - 2¹¹ = 1680589873 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1680591923) 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, 280098651 + ... + 280098656.

It is an arithmetic number, because the mean of its divisors is an integer number (560197308).

Almost surely, 2^1680591921 is an apocalyptic number.

It is an amenable number.

1680591921 is a deficient number, since it is larger than the sum of its proper divisors (560197311).

1680591921 is an equidigital number, since it uses as much as digits as its factorization.

1680591921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 560197310.

The product of its (nonzero) digits is 38880, while the sum is 42.

The square root of 1680591921 is about 40995.0231247648. The cubic root of 1680591921 is about 1188.9239905168.

The spelling of 1680591921 in words is "one billion, six hundred eighty million, five hundred ninety-one thousand, nine hundred twenty-one".