81504161 has 4 divisors (see below), whose sum is σ = 81522324. Its totient is φ = 81486000.

The previous prime is 81504151. The next prime is 81504169. The reversal of 81504161 is 16140518.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 70980625 + 10523536 = 8425^2 + 3244^2 .

It is a cyclic number.

It is not a de Polignac number, because 81504161 - 2⁶ = 81504097 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 81504161.

It is not an unprimeable number, because it can be changed into a prime (81504169) 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, 3071 + ... + 13131.

It is an arithmetic number, because the mean of its divisors is an integer number (20380581).

Almost surely, 2^81504161 is an apocalyptic number.

It is an amenable number.

81504161 is a deficient number, since it is larger than the sum of its proper divisors (18163).

81504161 is a wasteful number, since it uses less digits than its factorization.

81504161 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18162.

The product of its (nonzero) digits is 960, while the sum is 26.

The square root of 81504161 is about 9027.9654961680. The cubic root of 81504161 is about 433.5707014450.

Adding to 81504161 its reverse (16140518), we get a palindrome (97644679).

The spelling of 81504161 in words is "eighty-one million, five hundred four thousand, one hundred sixty-one".