19681639 has 2 divisors, whose sum is σ = 19681640. Its totient is φ = 19681638.

The previous prime is 19681637. The next prime is 19681661. The reversal of 19681639 is 93618691.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 19681639 - 2¹ = 19681637 is a prime.

Together with 19681637, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 19681595 and 19681604.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19681637) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9840819 + 9840820.

It is an arithmetic number, because the mean of its divisors is an integer number (9840820).

Almost surely, 2^19681639 is an apocalyptic number.

19681639 is a deficient number, since it is larger than the sum of its proper divisors (1).

19681639 is an equidigital number, since it uses as much as digits as its factorization.

19681639 is an evil number, because the sum of its binary digits is even.

The product of its digits is 69984, while the sum is 43.

The square root of 19681639 is about 4436.3993282841. The cubic root of 19681639 is about 269.9937767198.

The spelling of 19681639 in words is "nineteen million, six hundred eighty-one thousand, six hundred thirty-nine".