997666 has 4 divisors (see below), whose sum is σ = 1496502. Its totient is φ = 498832.

The previous prime is 997663. The next prime is 997681. The reversal of 997666 is 666799.

It is a happy number.

997666 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 666799 = 7 ⋅95257.

It can be written as a sum of positive squares in only one way, i.e., 594441 + 403225 = 771^2 + 635^2 .

It is an Ulam number.

It is a nialpdrome in base 10.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (997663) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 249415 + ... + 249418.

2⁹⁹⁷⁶⁶⁶ is an apocalyptic number.

997666 is a deficient number, since it is larger than the sum of its proper divisors (498836).

997666 is a wasteful number, since it uses less digits than its factorization.

997666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 498835.

The product of its digits is 122472, while the sum is 43.

The square root of 997666 is about 998.8323182597. The cubic root of 997666 is about 99.9221393930.

The spelling of 997666 in words is "nine hundred ninety-seven thousand, six hundred sixty-six".