19729475921 has 2 divisors, whose sum is σ = 19729475922. Its totient is φ = 19729475920.

The previous prime is 19729475897. The next prime is 19729475933. The reversal of 19729475921 is 12957492791.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19290154321 + 439321600 = 138889^2 + 20960^2 .

It is an emirp because it is prime and its reverse (12957492791) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-19729475921 is a prime.

It is not a weakly prime, because it can be changed into another prime (19729475951) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9864737960 + 9864737961.

It is an arithmetic number, because the mean of its divisors is an integer number (9864737961).

Almost surely, 2^19729475921 is an apocalyptic number.

It is an amenable number.

19729475921 is a deficient number, since it is larger than the sum of its proper divisors (1).

19729475921 is an equidigital number, since it uses as much as digits as its factorization.

19729475921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2857680, while the sum is 56.

The spelling of 19729475921 in words is "nineteen billion, seven hundred twenty-nine million, four hundred seventy-five thousand, nine hundred twenty-one".