19943639 has 2 divisors, whose sum is σ = 19943640. Its totient is φ = 19943638.

The previous prime is 19943611. The next prime is 19943659. The reversal of 19943639 is 93634991.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 19943639 - 2⁸ = 19943383 is a prime.

It is a Sophie Germain prime.

It is a self number, because there is not a number n which added to its sum of digits gives 19943639.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19943659) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9971819 + 9971820.

It is an arithmetic number, because the mean of its divisors is an integer number (9971820).

Almost surely, 2^19943639 is an apocalyptic number.

19943639 is a deficient number, since it is larger than the sum of its proper divisors (1).

19943639 is an equidigital number, since it uses as much as digits as its factorization.

19943639 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 157464, while the sum is 44.

The square root of 19943639 is about 4465.8301579885. The cubic root of 19943639 is about 271.1865429506.

The spelling of 19943639 in words is "nineteen million, nine hundred forty-three thousand, six hundred thirty-nine".