819968581 has 4 divisors (see below), whose sum is σ = 842129932. Its totient is φ = 797807232.

The previous prime is 819968573. The next prime is 819968587. The reversal of 819968581 is 185869918.

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 608411556 + 211557025 = 24666^2 + 14545^2 .

It is a cyclic number.

It is not a de Polignac number, because 819968581 - 2³ = 819968573 is a prime.

It is a super-2 number, since 2×819968581² = 1344696947654307122, 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 (819968587) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 11080620 + ... + 11080693.

It is an arithmetic number, because the mean of its divisors is an integer number (210532483).

Almost surely, 2^819968581 is an apocalyptic number.

It is an amenable number.

819968581 is a deficient number, since it is larger than the sum of its proper divisors (22161351).

819968581 is a wasteful number, since it uses less digits than its factorization.

819968581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22161350.

The product of its digits is 1244160, while the sum is 55.

The square root of 819968581 is about 28635.0935217610. The cubic root of 819968581 is about 935.9782077407.

The spelling of 819968581 in words is "eight hundred nineteen million, nine hundred sixty-eight thousand, five hundred eighty-one".