39 is the 12th distinct
semiprime[1] and the 4th in the (3.q) family.[2] It is the last member of the third distinct semiprime pair (
38,39).
39 has an
aliquot sum of
17, which is a prime. 39 is the 4th member of the
17-aliquot tree within an
aliquot sequence of one composite numbers (39,
17,
1,0) to the Prime in the
17-aliquot tree.
It is a
perfect totient number.[3] *39 is the sum of five consecutive
primes (3 + 5 + 7 + 11 + 13) and also is the product of the first and the last of those consecutive primes. Among small semiprimes only three other integers (10, 155, and 371) share this attribute. 39 also is the sum of the first three powers of
3 (31 + 32 + 33). Given 39, the
Mertens function returns
0.[4]
39 is the smallest natural number which has three
partitions into three parts which all give the same product when multiplied: {25, 8, 6}, {24, 10, 5}, {20, 15, 4}.
39 is a
Perrin number, coming after 17, 22, 29 (it is the sum of the first two mentioned).[5]
Since the greatest prime factor of 392 + 1 = 1522 is 761, which is more than 39 twice, 39 is a
Størmer number.[6]
39 is the 12th distinct
semiprime[1] and the 4th in the (3.q) family.[2] It is the last member of the third distinct semiprime pair (
38,39).
39 has an
aliquot sum of
17, which is a prime. 39 is the 4th member of the
17-aliquot tree within an
aliquot sequence of one composite numbers (39,
17,
1,0) to the Prime in the
17-aliquot tree.
It is a
perfect totient number.[3] *39 is the sum of five consecutive
primes (3 + 5 + 7 + 11 + 13) and also is the product of the first and the last of those consecutive primes. Among small semiprimes only three other integers (10, 155, and 371) share this attribute. 39 also is the sum of the first three powers of
3 (31 + 32 + 33). Given 39, the
Mertens function returns
0.[4]
39 is the smallest natural number which has three
partitions into three parts which all give the same product when multiplied: {25, 8, 6}, {24, 10, 5}, {20, 15, 4}.
39 is a
Perrin number, coming after 17, 22, 29 (it is the sum of the first two mentioned).[5]
Since the greatest prime factor of 392 + 1 = 1522 is 761, which is more than 39 twice, 39 is a
Størmer number.[6]