19991639 has 2 divisors, whose sum is σ = 19991640. Its totient is φ = 19991638.

The previous prime is 19991627. The next prime is 19991651. The reversal of 19991639 is 93619991.

It is a balanced prime because it is at equal distance from previous prime (19991627) and next prime (19991651).

It is a cyclic number.

It is not a de Polignac number, because 19991639 - 2¹² = 19987543 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 19991593 and 19991602.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19991039) 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, 9995819 + 9995820.

It is an arithmetic number, because the mean of its divisors is an integer number (9995820).

Almost surely, 2^19991639 is an apocalyptic number.

19991639 is a deficient number, since it is larger than the sum of its proper divisors (1).

19991639 is an equidigital number, since it uses as much as digits as its factorization.

19991639 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 118098, while the sum is 47.

The square root of 19991639 is about 4471.2010690641. The cubic root of 19991639 is about 271.4039309778.

The spelling of 19991639 in words is "nineteen million, nine hundred ninety-one thousand, six hundred thirty-nine".