81438569 has 4 divisors (see below), whose sum is σ = 81957444. Its totient is φ = 80919696.

The previous prime is 81438563. The next prime is 81438593. The reversal of 81438569 is 96583418.

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 30858025 + 50580544 = 5555^2 + 7112^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81438569 is a prime.

It is a super-2 number, since 2×81438569² = 13264481041535522, which contains 22 as substring.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81438563) 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, 259202 + ... + 259515.

It is an arithmetic number, because the mean of its divisors is an integer number (20489361).

Almost surely, 2^81438569 is an apocalyptic number.

It is an amenable number.

81438569 is a deficient number, since it is larger than the sum of its proper divisors (518875).

81438569 is a wasteful number, since it uses less digits than its factorization.

81438569 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 518874.

The product of its digits is 207360, while the sum is 44.

The square root of 81438569 is about 9024.3320528447. The cubic root of 81438569 is about 433.4543621833.

The spelling of 81438569 in words is "eighty-one million, four hundred thirty-eight thousand, five hundred sixty-nine".