81646533 has 6 divisors (see below), whose sum is σ = 117933894. Its totient is φ = 54431016.

The previous prime is 81646511. The next prime is 81646547. The reversal of 81646533 is 33564618.

81646533 is a `hidden beast` number, since 8 + 1 + 646 + 5 + 3 + 3 = 666.

It can be written as a sum of positive squares in only one way, i.e., 47983329 + 33663204 = 6927^2 + 5802^2 .

It is not a de Polignac number, because 81646533 - 2⁶ = 81646469 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81646583) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 4535910 + ... + 4535927.

It is an arithmetic number, because the mean of its divisors is an integer number (19655649).

Almost surely, 2^81646533 is an apocalyptic number.

It is an amenable number.

81646533 is a deficient number, since it is larger than the sum of its proper divisors (36287361).

81646533 is a wasteful number, since it uses less digits than its factorization.

81646533 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9071843 (or 9071840 counting only the distinct ones).

The product of its digits is 51840, while the sum is 36.

The square root of 81646533 is about 9035.8471102603. The cubic root of 81646533 is about 433.8230093006.

The spelling of 81646533 in words is "eighty-one million, six hundred forty-six thousand, five hundred thirty-three".