19729909 has 2 divisors, whose sum is σ = 19729910. Its totient is φ = 19729908.

The previous prime is 19729907. The next prime is 19729933. The reversal of 19729909 is 90992791.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16990884 + 2739025 = 4122^2 + 1655^2 .

It is a cyclic number.

It is not a de Polignac number, because 19729909 - 2¹ = 19729907 is a prime.

Together with 19729907, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19729903) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9864954 + 9864955.

It is an arithmetic number, because the mean of its divisors is an integer number (9864955).

Almost surely, 2^19729909 is an apocalyptic number.

It is an amenable number.

19729909 is a deficient number, since it is larger than the sum of its proper divisors (1).

19729909 is an equidigital number, since it uses as much as digits as its factorization.

19729909 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 91854, while the sum is 46.

The square root of 19729909 is about 4441.8362194030. The cubic root of 19729909 is about 270.2143200017.

It can be divided in two parts, 1972 and 9909, that added together give a square (11881 = 109²).

The spelling of 19729909 in words is "nineteen million, seven hundred twenty-nine thousand, nine hundred nine".