1640257405 has 4 divisors (see below), whose sum is σ = 1968308892. Its totient is φ = 1312205920.

The previous prime is 1640257379. The next prime is 1640257447. The reversal of 1640257405 is 5047520461.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 5047520461 = 36269 ⋅139169.

It can be written as a sum of positive squares in 2 ways, for example, as 1287230884 + 353026521 = 35878^2 + 18789^2 .

It is not a de Polignac number, because 1640257405 - 2²⁷ = 1506039677 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 164025736 + ... + 164025745.

It is an arithmetic number, because the mean of its divisors is an integer number (492077223).

Almost surely, 2^1640257405 is an apocalyptic number.

It is an amenable number.

1640257405 is a deficient number, since it is larger than the sum of its proper divisors (328051487).

1640257405 is an equidigital number, since it uses as much as digits as its factorization.

1640257405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 328051486.

The product of its (nonzero) digits is 33600, while the sum is 34.

The square root of 1640257405 is about 40500.0914196499. The cubic root of 1640257405 is about 1179.3354021138.

Adding to 1640257405 its reverse (5047520461), we get a palindrome (6687777866).

The spelling of 1640257405 in words is "one billion, six hundred forty million, two hundred fifty-seven thousand, four hundred five".