216531081 has 36 divisors (see below), whose sum is σ = 350426700. Its totient is φ = 128628864.

The previous prime is 216531071. The next prime is 216531083. The reversal of 216531081 is 180135612.

216531081 is a `hidden beast` number, since 2 + 1 + 653 + 1 + 0 + 8 + 1 = 666.

It can be written as a sum of positive squares in 6 ways, for example, as 176400 + 216354681 = 420^2 + 14709^2 .

It is not a de Polignac number, because 216531081 - 2⁷ = 216530953 is a prime.

It is a super-2 number, since 2×216531081² = 93771418078057122, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (216531083) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 41655 + ... + 46563.

It is an arithmetic number, because the mean of its divisors is an integer number (9734075).

Almost surely, 2^216531081 is an apocalyptic number.

It is an amenable number.

216531081 is a deficient number, since it is larger than the sum of its proper divisors (133895619).

216531081 is a wasteful number, since it uses less digits than its factorization.

216531081 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4970 (or 4954 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 27.

The square root of 216531081 is about 14714.9951070328. The cubic root of 216531081 is about 600.4913391998.

Adding to 216531081 its reverse (180135612), we get a palindrome (396666693).

The spelling of 216531081 in words is "two hundred sixteen million, five hundred thirty-one thousand, eighty-one".