81066581 has 4 divisors (see below), whose sum is σ = 83681664. Its totient is φ = 78451500.

The previous prime is 81066577. The next prime is 81066617. The reversal of 81066581 is 18566018.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 81066581 - 2² = 81066577 is a prime.

It is a super-2 number, since 2×81066581² = 13143581110059122, 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 (81066541) 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, 1307495 + ... + 1307556.

It is an arithmetic number, because the mean of its divisors is an integer number (20920416).

Almost surely, 2^81066581 is an apocalyptic number.

It is an amenable number.

81066581 is a deficient number, since it is larger than the sum of its proper divisors (2615083).

81066581 is a wasteful number, since it uses less digits than its factorization.

81066581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2615082.

The product of its (nonzero) digits is 11520, while the sum is 35.

The square root of 81066581 is about 9003.6981846350. The cubic root of 81066581 is about 432.7933897586.

The spelling of 81066581 in words is "eighty-one million, sixty-six thousand, five hundred eighty-one".