1680640393 has 4 divisors (see below), whose sum is σ = 1738593540. Its totient is φ = 1622687248.

The previous prime is 1680640327. The next prime is 1680640399. The reversal of 1680640393 is 3930460861.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 3930460861 = 2003 ⋅1962287.

It can be written as a sum of positive squares in 2 ways, for example, as 577537024 + 1103103369 = 24032^2 + 33213^2 .

It is a cyclic number.

It is not a de Polignac number, because 1680640393 - 2²¹ = 1678543241 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1680640399) 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, 28976530 + ... + 28976587.

It is an arithmetic number, because the mean of its divisors is an integer number (434648385).

Almost surely, 2^1680640393 is an apocalyptic number.

It is an amenable number.

1680640393 is a deficient number, since it is larger than the sum of its proper divisors (57953147).

1680640393 is an equidigital number, since it uses as much as digits as its factorization.

1680640393 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 57953146.

The product of its (nonzero) digits is 93312, while the sum is 40.

The square root of 1680640393 is about 40995.6143142166. The cubic root of 1680640393 is about 1188.9354208089.

The spelling of 1680640393 in words is "one billion, six hundred eighty million, six hundred forty thousand, three hundred ninety-three".