81705228 has 24 divisors (see below), whose sum is σ = 207977280. Its totient is φ = 24759120.

The previous prime is 81705191. The next prime is 81705229. The reversal of 81705228 is 82250718.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is not an unprimeable number, because it can be changed into a prime (81705229) 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, 309358 + ... + 309621.

It is an arithmetic number, because the mean of its divisors is an integer number (8665720).

Almost surely, 2^81705228 is an apocalyptic number.

It is an amenable number.

81705228 is an abundant number, since it is smaller than the sum of its proper divisors (126272052).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81705228 is a wasteful number, since it uses less digits than its factorization.

81705228 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 618997 (or 618995 counting only the distinct ones).

The product of its (nonzero) digits is 8960, while the sum is 33.

The square root of 81705228 is about 9039.0944236688. The cubic root of 81705228 is about 433.9269416264.

Subtracting 81705228 from its reverse (82250718), we obtain a triangular number (545490 = T₁₀₄₄).

The spelling of 81705228 in words is "eighty-one million, seven hundred five thousand, two hundred twenty-eight".