81561266 has 8 divisors (see below), whose sum is σ = 127661184. Its totient is φ = 39007540.

The previous prime is 81561229. The next prime is 81561269. The reversal of 81561266 is 66216518.

It is a happy number.

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

It is a super-2 number, since 2×81561266² = 13304480223045512, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (81561269) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 886490 + ... + 886581.

It is an arithmetic number, because the mean of its divisors is an integer number (15957648).

Almost surely, 2^81561266 is an apocalyptic number.

81561266 is a deficient number, since it is larger than the sum of its proper divisors (46099918).

81561266 is a wasteful number, since it uses less digits than its factorization.

81561266 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1773096.

The product of its digits is 17280, while the sum is 35.

The square root of 81561266 is about 9031.1276150877. The cubic root of 81561266 is about 433.6719366640.

The spelling of 81561266 in words is "eighty-one million, five hundred sixty-one thousand, two hundred sixty-six".