997778 has 8 divisors (see below), whose sum is σ = 1525068. Its totient is φ = 489424.

The previous prime is 997769. The next prime is 997783. The reversal of 997778 is 877799.

It can be written as a sum of positive squares in 2 ways, for example, as 779689 + 218089 = 883^2 + 467^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is an unprimeable number.

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 in 3 ways as a sum of consecutive naturals, for example, 4601 + ... + 4812.

2⁹⁹⁷⁷⁷⁸ is an apocalyptic number.

997778 is a deficient number, since it is larger than the sum of its proper divisors (527290).

997778 is a wasteful number, since it uses less digits than its factorization.

997778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9468.

The product of its digits is 222264, while the sum is 47.

The square root of 997778 is about 998.8883821529. Note that the first 3 decimals coincide. The cubic root of 997778 is about 99.9258784068.

It can be divided in two parts, 99777 and 8, that multiplied together give a triangular number (798216 = T₁₂₆₃).

The spelling of 997778 in words is "nine hundred ninety-seven thousand, seven hundred seventy-eight".