81161533 has 4 divisors (see below), whose sum is σ = 81920160. Its totient is φ = 80402908.

The previous prime is 81161513. The next prime is 81161543. The reversal of 81161533 is 33516118.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81161533 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81161513) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 379153 + ... + 379366.

It is an arithmetic number, because the mean of its divisors is an integer number (20480040).

Almost surely, 2^81161533 is an apocalyptic number.

It is an amenable number.

81161533 is a deficient number, since it is larger than the sum of its proper divisors (758627).

81161533 is a wasteful number, since it uses less digits than its factorization.

81161533 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 758626.

The product of its digits is 2160, while the sum is 28.

The square root of 81161533 is about 9008.9695859182. The cubic root of 81161533 is about 432.9622985058.

The spelling of 81161533 in words is "eighty-one million, one hundred sixty-one thousand, five hundred thirty-three".