81428 has 6 divisors (see below), whose sum is σ = 142506. Its totient is φ = 40712.

The previous prime is 81421. The next prime is 81439. The reversal of 81428 is 82418.

It can be written as a sum of positive squares in only one way, i.e., 71824 + 9604 = 268^2 + 98^2 .

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 81428.

It is not an unprimeable number, because it can be changed into a prime (81421) by changing a digit.

81428 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10175 + ... + 10182.

It is an arithmetic number, because the mean of its divisors is an integer number (23751).

2⁸¹⁴²⁸ is an apocalyptic number.

It is an amenable number.

81428 is a deficient number, since it is larger than the sum of its proper divisors (61078).

81428 is a wasteful number, since it uses less digits than its factorization.

81428 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20361 (or 20359 counting only the distinct ones).

The product of its digits is 512, while the sum is 23.

The square root of 81428 is about 285.3559181093. The cubic root of 81428 is about 43.3435610309.

Subtracting 81428 from its reverse (82418), we obtain a triangular number (990 = T₄₄).

The spelling of 81428 in words is "eighty-one thousand, four hundred twenty-eight".