1978874581 has 4 divisors (see below), whose sum is σ = 1984480812. Its totient is φ = 1973268352.

The previous prime is 1978874561. The next prime is 1978874591. The reversal of 1978874581 is 1854788791.

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

It can be written as a sum of positive squares in 2 ways, for example, as 1561040100 + 417834481 = 39510^2 + 20441^2 .

It is a cyclic number.

It is not a de Polignac number, because 1978874581 - 2⁵ = 1978874549 is a prime.

It is a super-2 number, since 2×1978874581² = 7831889214655851122, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1978874561) 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, 2802586 + ... + 2803291.

It is an arithmetic number, because the mean of its divisors is an integer number (496120203).

Almost surely, 2^1978874581 is an apocalyptic number.

It is an amenable number.

1978874581 is a deficient number, since it is larger than the sum of its proper divisors (5606231).

1978874581 is an equidigital number, since it uses as much as digits as its factorization.

1978874581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5606230.

The product of its digits is 4515840, while the sum is 58.

The square root of 1978874581 is about 44484.5431695100. The cubic root of 1978874581 is about 1255.4692786377.

The spelling of 1978874581 in words is "one billion, nine hundred seventy-eight million, eight hundred seventy-four thousand, five hundred eighty-one".