81011531 has 8 divisors (see below), whose sum is σ = 84127344. Its totient is φ = 77950080.

The previous prime is 81011521. The next prime is 81011549. The reversal of 81011531 is 13511018.

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 81011531 - 2¹⁰ = 81010507 is a prime.

It is a super-2 number, since 2×81011531² = 13125736309927922, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81011521) 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, 10541 + ... + 16526.

It is an arithmetic number, because the mean of its divisors is an integer number (10515918).

Almost surely, 2^81011531 is an apocalyptic number.

81011531 is a deficient number, since it is larger than the sum of its proper divisors (3115813).

81011531 is a wasteful number, since it uses less digits than its factorization.

81011531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27181.

The product of its (nonzero) digits is 120, while the sum is 20.

The square root of 81011531 is about 9000.6405883137. The cubic root of 81011531 is about 432.6954016980.

Adding to 81011531 its reverse (13511018), we get a palindrome (94522549).

The spelling of 81011531 in words is "eighty-one million, eleven thousand, five hundred thirty-one".