1643139209 has 4 divisors (see below), whose sum is σ = 1729620240. Its totient is φ = 1556658180.

The previous prime is 1643139191. The next prime is 1643139257. The reversal of 1643139209 is 9029313461.

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: 9029313461 = 7 ⋅1289901923.

It is a cyclic number.

It is not a de Polignac number, because 1643139209 - 2⁸ = 1643138953 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1643139259) 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, 43240487 + ... + 43240524.

It is an arithmetic number, because the mean of its divisors is an integer number (432405060).

Almost surely, 2^1643139209 is an apocalyptic number.

1643139209 is a gapful number since it is divisible by the number (19) formed by its first and last digit.

It is an amenable number.

1643139209 is a deficient number, since it is larger than the sum of its proper divisors (86481031).

1643139209 is an equidigital number, since it uses as much as digits as its factorization.

1643139209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 86481030.

The product of its (nonzero) digits is 34992, while the sum is 38.

The square root of 1643139209 is about 40535.6535533843. The cubic root of 1643139209 is about 1180.0256647200.

The spelling of 1643139209 in words is "one billion, six hundred forty-three million, one hundred thirty-nine thousand, two hundred nine".