81501281 has 8 divisors (see below), whose sum is σ = 89271720. Its totient is φ = 74061568.

The previous prime is 81501271. The next prime is 81501289. The reversal of 81501281 is 18210518.

It can be written as a sum of positive squares in 4 ways, for example, as 2202256 + 79299025 = 1484^2 + 8905^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81501281 is a prime.

It is a super-2 number, since 2×81501281² = 13284917609281922, which contains 22 as substring.

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 81501281.

It is not an unprimeable number, because it can be changed into a prime (81501289) 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, 82166 + ... + 83151.

It is an arithmetic number, because the mean of its divisors is an integer number (11158965).

Almost surely, 2^81501281 is an apocalyptic number.

It is an amenable number.

81501281 is a deficient number, since it is larger than the sum of its proper divisors (7770439).

81501281 is a wasteful number, since it uses less digits than its factorization.

81501281 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 165363.

The product of its (nonzero) digits is 640, while the sum is 26.

The square root of 81501281 is about 9027.8059903833. The cubic root of 81501281 is about 433.5655945551.

Adding to 81501281 its reverse (18210518), we get a palindrome (99711799).

The spelling of 81501281 in words is "eighty-one million, five hundred one thousand, two hundred eighty-one".