1978561 has 4 divisors (see below), whose sum is σ = 2130772. Its totient is φ = 1826352.

The previous prime is 1978541. The next prime is 1978567. The reversal of 1978561 is 1658791.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1658791 = 271 ⋅6121.

It can be written as a sum of positive squares in 2 ways, for example, as 810000 + 1168561 = 900^2 + 1081^2 .

It is a cyclic number.

It is not a de Polignac number, because 1978561 - 2⁷ = 1978433 is a prime.

It is a Duffinian number.

1978561 is a lucky number.

It is a self number, because there is not a number n which added to its sum of digits gives 1978561.

It is not an unprimeable number, because it can be changed into a prime (1978567) 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, 76086 + ... + 76111.

It is an arithmetic number, because the mean of its divisors is an integer number (532693).

2^1978561 is an apocalyptic number.

It is an amenable number.

1978561 is a deficient number, since it is larger than the sum of its proper divisors (152211).

1978561 is a wasteful number, since it uses less digits than its factorization.

1978561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 152210.

The product of its digits is 15120, while the sum is 37.

The square root of 1978561 is about 1406.6133086247. The cubic root of 1978561 is about 125.5402959442.

The spelling of 1978561 in words is "one million, nine hundred seventy-eight thousand, five hundred sixty-one".