281820 has 96 divisors (see below), whose sum is σ = 999936. Its totient is φ = 57600.

The previous prime is 281807. The next prime is 281833. The reversal of 281820 is 28182.

281820 = T₆₄ + T₆₅ + ... + T₁₂₄.

It is an interprime number because it is at equal distance from previous prime (281807) and next prime (281833).

It is a super-3 number, since 3×281820³ = 67148557333704000, which contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a congruent number.

It is an unprimeable number.

281820 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 in 31 ways as a sum of consecutive naturals, for example, 4590 + ... + 4650.

It is an arithmetic number, because the mean of its divisors is an integer number (10416).

2²⁸¹⁸²⁰ is an apocalyptic number.

281820 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 281820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (499968).

281820 is an abundant number, since it is smaller than the sum of its proper divisors (718116).

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

281820 is a wasteful number, since it uses less digits than its factorization.

281820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 91 (or 89 counting only the distinct ones).

The product of its (nonzero) digits is 256, while the sum is 21.

The square root of 281820 is about 530.8672150359. The cubic root of 281820 is about 65.5627663980.

The spelling of 281820 in words is "two hundred eighty-one thousand, eight hundred twenty".