81228561 has 8 divisors (see below), whose sum is σ = 108376320. Its totient is φ = 54116592.

The previous prime is 81228559. The next prime is 81228569. The reversal of 81228561 is 16582218.

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

It is not a de Polignac number, because 81228561 - 2¹ = 81228559 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81228569) 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, 3105 + ... + 13118.

It is an arithmetic number, because the mean of its divisors is an integer number (13547040).

Almost surely, 2^81228561 is an apocalyptic number.

It is an amenable number.

81228561 is a deficient number, since it is larger than the sum of its proper divisors (27147759).

81228561 is a wasteful number, since it uses less digits than its factorization.

81228561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17895.

The product of its digits is 7680, while the sum is 33.

The square root of 81228561 is about 9012.6888884505. The cubic root of 81228561 is about 433.0814543446.

The spelling of 81228561 in words is "eighty-one million, two hundred twenty-eight thousand, five hundred sixty-one".