19997806 has 4 divisors (see below), whose sum is σ = 29996712. Its totient is φ = 9998902.

The previous prime is 19997779. The next prime is 19997807. The reversal of 19997806 is 60879991.

It is a semiprime because it is the product of two primes.

It is a Smith number, since the sum of its digits (49) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a self number, because there is not a number n which added to its sum of digits gives 19997806.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19997807) 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, 4999450 + ... + 4999453.

It is an arithmetic number, because the mean of its divisors is an integer number (7499178).

Almost surely, 2^19997806 is an apocalyptic number.

19997806 is a deficient number, since it is larger than the sum of its proper divisors (9998906).

19997806 is an equidigital number, since it uses as much as digits as its factorization.

19997806 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9998905.

The product of its (nonzero) digits is 244944, while the sum is 49.

The square root of 19997806 is about 4471.8906516148. The cubic root of 19997806 is about 271.4318355761.

The spelling of 19997806 in words is "nineteen million, nine hundred ninety-seven thousand, eight hundred six".