81585749 has 32 divisors (see below), whose sum is σ = 100024320. Its totient is φ = 65100672.

The previous prime is 81585743. The next prime is 81585767. The reversal of 81585749 is 94758518.

It is not a de Polignac number, because 81585749 - 2²⁰ = 80537173 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (47).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81585743) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1032692 + ... + 1032770.

It is an arithmetic number, because the mean of its divisors is an integer number (3125760).

Almost surely, 2^81585749 is an apocalyptic number.

It is an amenable number.

81585749 is a deficient number, since it is larger than the sum of its proper divisors (18438571).

81585749 is a wasteful number, since it uses less digits than its factorization.

81585749 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 249.

The product of its digits is 403200, while the sum is 47.

The square root of 81585749 is about 9032.4829919574. The cubic root of 81585749 is about 433.7153254290.

The spelling of 81585749 in words is "eighty-one million, five hundred eighty-five thousand, seven hundred forty-nine".