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221991 = 3711312
BaseRepresentation
bin110110001100100111
3102021111220
4312030213
524100431
64431423
71613130
oct661447
9367456
10221991
11141870
12a8573
137a073
145ac87
1545b96
hex36327

221991 has 24 divisors (see below), whose sum is σ = 381312. Its totient is φ = 111600.

The previous prime is 221989. The next prime is 221999. The reversal of 221991 is 199122.

221991 is nontrivially palindromic in base 4.

It is not a de Polignac number, because 221991 - 21 = 221989 is a prime.

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 221991.

It is not an unprimeable number, because it can be changed into a prime (221999) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 7146 + ... + 7176.

It is an arithmetic number, because the mean of its divisors is an integer number (15888).

2221991 is an apocalyptic number.

221991 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

221991 is a deficient number, since it is larger than the sum of its proper divisors (159321).

221991 is a wasteful number, since it uses less digits than its factorization.

221991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 83 (or 52 counting only the distinct ones).

The product of its digits is 324, while the sum is 24.

The square root of 221991 is about 471.1592087607. The cubic root of 221991 is about 60.5496712042.

The spelling of 221991 in words is "two hundred twenty-one thousand, nine hundred ninety-one".

Divisors: 1 3 7 11 21 31 33 77 93 217 231 341 651 961 1023 2387 2883 6727 7161 10571 20181 31713 73997 221991