1643872949 has 2 divisors, whose sum is σ = 1643872950. Its totient is φ = 1643872948.

The previous prime is 1643872933. The next prime is 1643872961. The reversal of 1643872949 is 9492783461.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1409476849 + 234396100 = 37543^2 + 15310^2 .

It is a cyclic number.

It is not a de Polignac number, because 1643872949 - 2⁴ = 1643872933 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 1643872949.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1643872969) by changing a digit.

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 as a sum of consecutive naturals, namely, 821936474 + 821936475.

It is an arithmetic number, because the mean of its divisors is an integer number (821936475).

Almost surely, 2^1643872949 is an apocalyptic number.

It is an amenable number.

1643872949 is a deficient number, since it is larger than the sum of its proper divisors (1).

1643872949 is an equidigital number, since it uses as much as digits as its factorization.

1643872949 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2612736, while the sum is 53.

The square root of 1643872949 is about 40544.7030942391. The cubic root of 1643872949 is about 1180.2012844889.

The spelling of 1643872949 in words is "one billion, six hundred forty-three million, eight hundred seventy-two thousand, nine hundred forty-nine".