221780 has 24 divisors (see below), whose sum is σ = 502152. Its totient is φ = 81792.

The previous prime is 221773. The next prime is 221797. The reversal of 221780 is 87122.

221780 = T₆ + T₇ + ... + T₁₀₉.

It can be written as a sum of positive squares in 4 ways, for example, as 4624 + 217156 = 68^2 + 466^2 .

It is a Harshad number since it is a multiple of its sum of digits (20).

It is an Ulam number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 167 + ... + 686.

It is an arithmetic number, because the mean of its divisors is an integer number (20923).

2²²¹⁷⁸⁰ is an apocalyptic number.

221780 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

221780 is an abundant number, since it is smaller than the sum of its proper divisors (280372).

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

221780 is a wasteful number, since it uses less digits than its factorization.

221780 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 875 (or 873 counting only the distinct ones).

The product of its (nonzero) digits is 224, while the sum is 20.

The square root of 221780 is about 470.9352397092. The cubic root of 221780 is about 60.5304811911.

It can be divided in two parts, 221 and 780, that added together give a palindrome (1001).

The spelling of 221780 in words is "two hundred twenty-one thousand, seven hundred eighty".