81581945 has 8 divisors (see below), whose sum is σ = 99078336. Its totient is φ = 64478896.

The previous prime is 81581917. The next prime is 81582023. The reversal of 81581945 is 54918518.

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 81581945 - 2²² = 77387641 is a prime.

It is a super-2 number, since 2×81581945² = 13311227499966050, which contains 22 as substring.

It is a Duffinian number.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 97877 + ... + 98706.

It is an arithmetic number, because the mean of its divisors is an integer number (12384792).

Almost surely, 2^81581945 is an apocalyptic number.

It is an amenable number.

81581945 is a deficient number, since it is larger than the sum of its proper divisors (17496391).

81581945 is a wasteful number, since it uses less digits than its factorization.

81581945 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 196671.

The product of its digits is 57600, while the sum is 41.

The square root of 81581945 is about 9032.2724161752. The cubic root of 81581945 is about 433.7085845510.

The spelling of 81581945 in words is "eighty-one million, five hundred eighty-one thousand, nine hundred forty-five".