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121991 = 432837
BaseRepresentation
bin11101110010000111
320012100012
4131302013
512400431
62340435
71015442
oct356207
9205305
10121991
1183721
125a71b
13436ac
1432659
152622b
hex1dc87

121991 has 4 divisors (see below), whose sum is σ = 124872. Its totient is φ = 119112.

The previous prime is 121967. The next prime is 121993. The reversal of 121991 is 199121.

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 121991 - 214 = 105607 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (121993) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1376 + ... + 1461.

It is an arithmetic number, because the mean of its divisors is an integer number (31218).

2121991 is an apocalyptic number.

121991 is a deficient number, since it is larger than the sum of its proper divisors (2881).

121991 is an equidigital number, since it uses as much as digits as its factorization.

121991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2880.

The product of its digits is 162, while the sum is 23.

The square root of 121991 is about 349.2721002313. The cubic root of 121991 is about 49.5955370161.

It can be divided in two parts, 121 and 991, that multiplied together give a palindrome (119911).

The spelling of 121991 in words is "one hundred twenty-one thousand, nine hundred ninety-one".

Divisors: 1 43 2837 121991