19990639 has 2 divisors, whose sum is σ = 19990640. Its totient is φ = 19990638.

The previous prime is 19990637. The next prime is 19990643. The reversal of 19990639 is 93609991.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 19990639 - 2¹ = 19990637 is a prime.

Together with 19990637, 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 (19990637) 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, 9995319 + 9995320.

It is an arithmetic number, because the mean of its divisors is an integer number (9995320).

Almost surely, 2^19990639 is an apocalyptic number.

19990639 is a deficient number, since it is larger than the sum of its proper divisors (1).

19990639 is an equidigital number, since it uses as much as digits as its factorization.

19990639 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 118098, while the sum is 46.

The square root of 19990639 is about 4471.0892408897. The cubic root of 19990639 is about 271.3994056117.

The spelling of 19990639 in words is "nineteen million, nine hundred ninety thousand, six hundred thirty-nine".