78861581 has 4 divisors (see below), whose sum is σ = 79064700. Its totient is φ = 78658464.

The previous prime is 78861577. The next prime is 78861599. The reversal of 78861581 is 18516887.

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 51351556 + 27510025 = 7166^2 + 5245^2 .

It is a cyclic number.

It is not a de Polignac number, because 78861581 - 2² = 78861577 is a prime.

It is a super-2 number, since 2×78861581² = 12438297915639122, 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 (78861281) by changing a digit.

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 in 3 ways as a sum of consecutive naturals, for example, 100976 + ... + 101753.

It is an arithmetic number, because the mean of its divisors is an integer number (19766175).

Almost surely, 2^78861581 is an apocalyptic number.

It is an amenable number.

78861581 is a deficient number, since it is larger than the sum of its proper divisors (203119).

78861581 is a wasteful number, since it uses less digits than its factorization.

78861581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 203118.

The product of its digits is 107520, while the sum is 44.

The square root of 78861581 is about 8880.4043263806. The cubic root of 78861581 is about 428.8332911988.

The spelling of 78861581 in words is "seventy-eight million, eight hundred sixty-one thousand, five hundred eighty-one".