81581001 has 8 divisors (see below), whose sum is σ = 108829344. Its totient is φ = 54360000.

The previous prime is 81580991. The next prime is 81581029. The reversal of 81581001 is 10018518.

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

It is not a de Polignac number, because 81581001 - 2⁵ = 81580969 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81581051) 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, 1626 + ... + 12876.

It is an arithmetic number, because the mean of its divisors is an integer number (13603668).

Almost surely, 2^81581001 is an apocalyptic number.

It is an amenable number.

81581001 is a deficient number, since it is larger than the sum of its proper divisors (27248343).

81581001 is a wasteful number, since it uses less digits than its factorization.

81581001 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13671.

The product of its (nonzero) digits is 320, while the sum is 24.

The square root of 81581001 is about 9032.2201589642. The cubic root of 81581001 is about 433.7069117034.

Adding to 81581001 its reverse (10018518), we get a palindrome (91599519).

The spelling of 81581001 in words is "eighty-one million, five hundred eighty-one thousand, one".