81432569 has 4 divisors (see below), whose sum is σ = 81450660. Its totient is φ = 81414480.

The previous prime is 81432553. The next prime is 81432577. The reversal of 81432569 is 96523418.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 96523418 = 2 ⋅48261709.

It can be written as a sum of positive squares in 2 ways, for example, as 3763600 + 77668969 = 1940^2 + 8813^2 .

It is a cyclic number.

It is not a de Polignac number, because 81432569 - 2⁴ = 81432553 is a prime.

It is a super-2 number, since 2×81432569² = 13262526587879522, 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 (81432509) 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, 3599 + ... + 13259.

It is an arithmetic number, because the mean of its divisors is an integer number (20362665).

Almost surely, 2^81432569 is an apocalyptic number.

It is an amenable number.

81432569 is a deficient number, since it is larger than the sum of its proper divisors (18091).

81432569 is an equidigital number, since it uses as much as digits as its factorization.

81432569 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18090.

The product of its digits is 51840, while the sum is 38.

The square root of 81432569 is about 9023.9996121454. Note that the first 3 decimals coincide. The cubic root of 81432569 is about 433.4437169813.

The spelling of 81432569 in words is "eighty-one million, four hundred thirty-two thousand, five hundred sixty-nine".