81564643 has 8 divisors (see below), whose sum is σ = 82525968. Its totient is φ = 80607744.

The previous prime is 81564631. The next prime is 81564653. The reversal of 81564643 is 34646518.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81564643 - 2⁵ = 81564611 is a prime.

It is a super-3 number, since 3×81564643³ (a number of 25 digits) contains 333 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81564653) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 48096 + ... + 49762.

It is an arithmetic number, because the mean of its divisors is an integer number (10315746).

Almost surely, 2^81564643 is an apocalyptic number.

81564643 is a deficient number, since it is larger than the sum of its proper divisors (961325).

81564643 is a wasteful number, since it uses less digits than its factorization.

81564643 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2213.

The product of its digits is 69120, while the sum is 37.

The square root of 81564643 is about 9031.3145776238. The cubic root of 81564643 is about 433.6779218985.

It can be divided in two parts, 8 and 1564643, that added together give a palindrome (1564651).

The spelling of 81564643 in words is "eighty-one million, five hundred sixty-four thousand, six hundred forty-three".