81002781 has 8 divisors (see below), whose sum is σ = 120004160. Its totient is φ = 54001836.

The previous prime is 81002777. The next prime is 81002791. The reversal of 81002781 is 18720018.

It is not a de Polignac number, because 81002781 - 2² = 81002777 is a prime.

It is a super-2 number, since 2×81002781² = 13122901059467922, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27), and also a Moran number because the ratio is a prime number: 3000103 = 81002781 / (8 + 1 + 0 + 0 + 2 + 7 + 8 + 1).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81002741) 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, 1500025 + ... + 1500078.

It is an arithmetic number, because the mean of its divisors is an integer number (15000520).

Almost surely, 2^81002781 is an apocalyptic number.

It is an amenable number.

81002781 is a deficient number, since it is larger than the sum of its proper divisors (39001379).

81002781 is a wasteful number, since it uses less digits than its factorization.

81002781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3000112 (or 3000106 counting only the distinct ones).

The product of its (nonzero) digits is 896, while the sum is 27.

The square root of 81002781 is about 9000.1544986739. The cubic root of 81002781 is about 432.6798227591.

Adding to 81002781 its reverse (18720018), we get a palindrome (99722799).

The spelling of 81002781 in words is "eighty-one million, two thousand, seven hundred eighty-one".