19997647 has 6 divisors (see below), whose sum is σ = 20288384. Its totient is φ = 19711020.

The previous prime is 19997641. The next prime is 19997657. The reversal of 19997647 is 74679991.

It is a de Polignac number, because none of the positive numbers 2^k-19997647 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 19997594 and 19997603.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19997641) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 3058 + ... + 7024.

Almost surely, 2^19997647 is an apocalyptic number.

19997647 is a deficient number, since it is larger than the sum of its proper divisors (290737).

19997647 is an frugal number, since it uses more digits than its factorization.

19997647 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4109 (or 4038 counting only the distinct ones).

The product of its digits is 857304, while the sum is 52.

The square root of 19997647 is about 4471.8728738639. The cubic root of 19997647 is about 271.4311162009.

The spelling of 19997647 in words is "nineteen million, nine hundred ninety-seven thousand, six hundred forty-seven".