19993997 has 2 divisors, whose sum is σ = 19993998. Its totient is φ = 19993996.

The previous prime is 19993951. The next prime is 19993999. The reversal of 19993997 is 79939991.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19945156 + 48841 = 4466^2 + 221^2 .

It is an emirp because it is prime and its reverse (79939991) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 19993997 - 2¹⁴ = 19977613 is a prime.

Together with 19993999, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19993999) 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, 9996998 + 9996999.

It is an arithmetic number, because the mean of its divisors is an integer number (9996999).

Almost surely, 2^19993997 is an apocalyptic number.

It is an amenable number.

19993997 is a deficient number, since it is larger than the sum of its proper divisors (1).

19993997 is an equidigital number, since it uses as much as digits as its factorization.

19993997 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1240029, while the sum is 56.

The square root of 19993997 is about 4471.4647488267. The cubic root of 19993997 is about 271.4146011937.

It can be divided in two parts, 1999 and 3997, that multiplied together give a triangular number (7990003 = T₃₉₉₇).

The spelling of 19993997 in words is "nineteen million, nine hundred ninety-three thousand, nine hundred ninety-seven".