81228781 has 8 divisors (see below), whose sum is σ = 86954400. Its totient is φ = 75648240.

The previous prime is 81228769. The next prime is 81228793. The reversal of 81228781 is 18782218.

It is an interprime number because it is at equal distance from previous prime (81228769) and next prime (81228793).

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

It is a cyclic number.

It is not a de Polignac number, because 81228781 - 2⁹ = 81228269 is a prime.

It is a super-2 number, since 2×81228781² = 13196229725491922, 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 81228781.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81228731) 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, 35110 + ... + 37351.

It is an arithmetic number, because the mean of its divisors is an integer number (10869300).

Almost surely, 2^81228781 is an apocalyptic number.

It is an amenable number.

81228781 is a deficient number, since it is larger than the sum of its proper divisors (5725619).

81228781 is a wasteful number, since it uses less digits than its factorization.

81228781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 72539.

The product of its digits is 14336, while the sum is 37.

The square root of 81228781 is about 9012.7010934569. The cubic root of 81228781 is about 433.0818453312.

The spelling of 81228781 in words is "eighty-one million, two hundred twenty-eight thousand, seven hundred eighty-one".