997978 has 4 divisors (see below), whose sum is σ = 1496970. Its totient is φ = 498988.

The previous prime is 997973. The next prime is 997991. The reversal of 997978 is 879799.

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

It can be written as a sum of positive squares in only one way, i.e., 994009 + 3969 = 997^2 + 63^2 .

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 not an unprimeable number, because it can be changed into a prime (997973) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 249493 + ... + 249496.

2⁹⁹⁷⁹⁷⁸ is an apocalyptic number.

997978 is a deficient number, since it is larger than the sum of its proper divisors (498992).

997978 is a wasteful number, since it uses less digits than its factorization.

997978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 498991.

The product of its digits is 285768, while the sum is 49.

The square root of 997978 is about 998.9884884222. The cubic root of 997978 is about 99.9325545213.

The spelling of 997978 in words is "nine hundred ninety-seven thousand, nine hundred seventy-eight".