It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 7999991 = 967 ⋅8273.
It is a cyclic number.
It is a Duffinian number.
It is a plaindrome in base 11.
It is a congruent number.
21999997 is an apocalyptic number.
It is an amenable number.
1999997 is a wasteful number, since it uses less digits than its factorization.
1999997 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 105282.
The square root of 1999997 is about 1414.2125017125. The cubic root of 1999997 is about 125.9920419934.
The spelling of 1999997 in words is "one million, nine hundred ninety-nine thousand, nine hundred ninety-seven".