19921439 has 2 divisors, whose sum is σ = 19921440. Its totient is φ = 19921438.

The previous prime is 19921423. The next prime is 19921453. The reversal of 19921439 is 93412991.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 19921439 - 2⁴ = 19921423 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19921939) 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, 9960719 + 9960720.

It is an arithmetic number, because the mean of its divisors is an integer number (9960720).

Almost surely, 2^19921439 is an apocalyptic number.

19921439 is a deficient number, since it is larger than the sum of its proper divisors (1).

19921439 is an equidigital number, since it uses as much as digits as its factorization.

19921439 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 17496, while the sum is 38.

The square root of 19921439 is about 4463.3439258027. The cubic root of 19921439 is about 271.0858830116.

The spelling of 19921439 in words is "nineteen million, nine hundred twenty-one thousand, four hundred thirty-nine".