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129991 = 612131
BaseRepresentation
bin11111101111000111
320121022111
4133233013
513124431
62441451
71050661
oct375707
9217274
10129991
1189734
1263287
1347224
1435531
15287b1
hex1fbc7

129991 has 4 divisors (see below), whose sum is σ = 132184. Its totient is φ = 127800.

The previous prime is 129971. The next prime is 130003. The reversal of 129991 is 199921.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 129991 - 25 = 129959 is a prime.

It is a Duffinian number.

129991 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (129901) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1005 + ... + 1126.

It is an arithmetic number, because the mean of its divisors is an integer number (33046).

2129991 is an apocalyptic number.

129991 is a deficient number, since it is larger than the sum of its proper divisors (2193).

129991 is an equidigital number, since it uses as much as digits as its factorization.

129991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2192.

The product of its digits is 1458, while the sum is 31.

The square root of 129991 is about 360.5426465760. The cubic root of 129991 is about 50.6568011339.

It can be divided in two parts, 1 and 29991, that added together give a palindrome (29992).

The spelling of 129991 in words is "one hundred twenty-nine thousand, nine hundred ninety-one".

Divisors: 1 61 2131 129991