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BaseRepresentation
bin10011000101
31200020
4103011
514341
65353
73363
oct2305
91606
101221
11a10
12859
1372c
14633
15566
hex4c5

1221 has 8 divisors (see below), whose sum is σ = 1824. Its totient is φ = 720.

The previous prime is 1217. The next prime is 1223.

It is a happy number.

1221 is nontrivially palindromic in base 5 and base 10.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 1221 - 22 = 1217 is a prime.

1221 is an undulating number in base 6.

It is a plaindrome in base 15.

It is a nialpdrome in base 11 and base 14.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1223) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 15 + ... + 51.

It is an arithmetic number, because the mean of its divisors is an integer number (228).

1221 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1221 is a deficient number, since it is larger than the sum of its proper divisors (603).

1221 is a wasteful number, since it uses less digits than its factorization.

1221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 51.

The product of its digits is 4, while the sum is 6.

The square root of 1221 is about 34.9428104193. The cubic root of 1221 is about 10.6882159843.

It can be divided in two parts, 12 and 21, that multiplied together give a palindrome (252).

The spelling of 1221 in words is "one thousand, two hundred twenty-one", and thus it is an iban number.

Divisors: 1 3 11 33 37 111 407 1221