1997978 has 4 divisors (see below), whose sum is σ = 2996970. Its totient is φ = 998988.

The previous prime is 1997969. The next prime is 1997999. The reversal of 1997978 is 8797991.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 8797991 = 29 ⋅303379.

It can be written as a sum of positive squares in only one way, i.e., 1545049 + 452929 = 1243^2 + 673^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 499493 + ... + 499496.

2^1997978 is an apocalyptic number.

1997978 is a deficient number, since it is larger than the sum of its proper divisors (998992).

1997978 is an equidigital number, since it uses as much as digits as its factorization.

1997978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 998991.

The product of its digits is 285768, while the sum is 50.

The square root of 1997978 is about 1413.4984966387. The cubic root of 1997978 is about 125.9496313333.

The spelling of 1997978 in words is "one million, nine hundred ninety-seven thousand, nine hundred seventy-eight".