81531861 has 8 divisors (see below), whose sum is σ = 110760480. Its totient is φ = 53328912.

The previous prime is 81531859. The next prime is 81531889. The reversal of 81531861 is 16813518.

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

It is not a de Polignac number, because 81531861 - 2¹ = 81531859 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81531061) 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, 256231 + ... + 256548.

It is an arithmetic number, because the mean of its divisors is an integer number (13845060).

Almost surely, 2^81531861 is an apocalyptic number.

It is an amenable number.

81531861 is a deficient number, since it is larger than the sum of its proper divisors (29228619).

81531861 is a wasteful number, since it uses less digits than its factorization.

81531861 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 512835.

The product of its digits is 5760, while the sum is 33.

The square root of 81531861 is about 9029.4994877900. The cubic root of 81531861 is about 433.6198136538.

The spelling of 81531861 in words is "eighty-one million, five hundred thirty-one thousand, eight hundred sixty-one".