81002881 has 4 divisors (see below), whose sum is σ = 81063252. Its totient is φ = 80942512.

The previous prime is 81002869. The next prime is 81002897. The reversal of 81002881 is 18820018.

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 66977856 + 14025025 = 8184^2 + 3745^2 .

It is a cyclic number.

It is not a de Polignac number, because 81002881 - 2¹³ = 80994689 is a prime.

It is a super-2 number, since 2×81002881² = 13122933460600322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81002821) 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, 28126 + ... + 30871.

It is an arithmetic number, because the mean of its divisors is an integer number (20265813).

Almost surely, 2^81002881 is an apocalyptic number.

It is an amenable number.

81002881 is a deficient number, since it is larger than the sum of its proper divisors (60371).

81002881 is a wasteful number, since it uses less digits than its factorization.

81002881 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 60370.

The product of its (nonzero) digits is 1024, while the sum is 28.

The square root of 81002881 is about 9000.1600541324. The cubic root of 81002881 is about 432.6800008104.

Adding to 81002881 its reverse (18820018), we get a palindrome (99822899).

The spelling of 81002881 in words is "eighty-one million, two thousand, eight hundred eighty-one".