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19951 = 71281
BaseRepresentation
bin100110111101111
31000100221
410313233
51114301
6232211
7112111
oct46757
930327
1019951
1113a98
12b667
139109
1473b1
155da1
hex4def

19951 has 4 divisors (see below), whose sum is σ = 20304. Its totient is φ = 19600.

The previous prime is 19949. The next prime is 19961. The reversal of 19951 is 15991.

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

It is a 4-Lehmer number, since φ(19951) divides (19951-1)4.

It is a cyclic number.

It is not a de Polignac number, because 19951 - 21 = 19949 is a prime.

It is a Duffinian number.

It is a plaindrome in base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19961) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 70 + ... + 211.

It is an arithmetic number, because the mean of its divisors is an integer number (5076).

It is a Poulet number, since it divides 219950-1.

219951 is an apocalyptic number.

19951 is the 71-st decagonal number.

19951 is the 76-th centered heptagonal number.

19951 is a deficient number, since it is larger than the sum of its proper divisors (353).

19951 is an equidigital number, since it uses as much as digits as its factorization.

19951 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 352.

The product of its digits is 405, while the sum is 25.

The square root of 19951 is about 141.2480088355. The cubic root of 19951 is about 27.1219902937.

The spelling of 19951 in words is "nineteen thousand, nine hundred fifty-one".

Divisors: 1 71 281 19951