19999897 has 2 divisors, whose sum is σ = 19999898. Its totient is φ = 19999896.

The previous prime is 19999891. The next prime is 19999909. The reversal of 19999897 is 79899991.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17106496 + 2893401 = 4136^2 + 1701^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-19999897 is a prime.

It is not a weakly prime, because it can be changed into another prime (19999891) 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, 9999948 + 9999949.

It is an arithmetic number, because the mean of its divisors is an integer number (9999949).

Almost surely, 2^19999897 is an apocalyptic number.

It is an amenable number.

19999897 is a deficient number, since it is larger than the sum of its proper divisors (1).

19999897 is an equidigital number, since it uses as much as digits as its factorization.

19999897 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3306744, while the sum is 61.

The square root of 19999897 is about 4472.1244392347. The cubic root of 19999897 is about 271.4412956837.

The spelling of 19999897 in words is "nineteen million, nine hundred ninety-nine thousand, eight hundred ninety-seven".