81731145 has 8 divisors (see below), whose sum is σ = 130769856. Its totient is φ = 43589936.

The previous prime is 81731131. The next prime is 81731147. The reversal of 81731145 is 54113718.

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 81731145 - 2⁴ = 81731129 is a prime.

It is a super-2 number, since 2×81731145² = 13359960126022050, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (81731147) 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, 2724357 + ... + 2724386.

It is an arithmetic number, because the mean of its divisors is an integer number (16346232).

Almost surely, 2^81731145 is an apocalyptic number.

It is an amenable number.

81731145 is a deficient number, since it is larger than the sum of its proper divisors (49038711).

81731145 is a wasteful number, since it uses less digits than its factorization.

81731145 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5448751.

The product of its digits is 3360, while the sum is 30.

The square root of 81731145 is about 9040.5279160014. The cubic root of 81731145 is about 433.9728174980.

Adding to 81731145 its product of digits (3360), we get a triangular number (81734505 = T₁₂₇₈₅).

The spelling of 81731145 in words is "eighty-one million, seven hundred thirty-one thousand, one hundred forty-five".