1978791 has 4 divisors (see below), whose sum is σ = 2638392. Its totient is φ = 1319192.

The previous prime is 1978771. The next prime is 1978799.

It is a happy number.

1978791 is nontrivially palindromic in base 10.

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

It is a cyclic number.

It is not a de Polignac number, because 1978791 - 2⁶ = 1978727 is a prime.

It is a super-2 number, since 2×1978791² = 7831227643362, which contains 22 as substring.

It is a D-number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1978799) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 329796 + ... + 329801.

It is an arithmetic number, because the mean of its divisors is an integer number (659598).

2^1978791 is an apocalyptic number.

1978791 is a deficient number, since it is larger than the sum of its proper divisors (659601).

1978791 is an equidigital number, since it uses as much as digits as its factorization.

1978791 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 659600.

The product of its digits is 31752, while the sum is 42.

The square root of 1978791 is about 1406.6950629045. The cubic root of 1978791 is about 125.5451602790.

The spelling of 1978791 in words is "one million, nine hundred seventy-eight thousand, seven hundred ninety-one".