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15661 is a prime number
BaseRepresentation
bin11110100101101
3210111001
43310231
51000121
6200301
763442
oct36455
923431
1015661
1110848
129091
137189
1459c9
154991
hex3d2d

15661 has 2 divisors, whose sum is σ = 15662. Its totient is φ = 15660.

The previous prime is 15649. The next prime is 15667. The reversal of 15661 is 16651.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15625 + 36 = 125^2 + 6^2 .

It is an emirp because it is prime and its reverse (16651) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 15661 - 25 = 15629 is a prime.

It is an Ulam number.

15661 is a lucky number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (15667) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7830 + 7831.

It is an arithmetic number, because the mean of its divisors is an integer number (7831).

15661 is a Friedman number, since it can be written as 6^(1+1)+5^6, using all its digits and the basic arithmetic operations.

215661 is an apocalyptic number.

It is an amenable number.

15661 is a deficient number, since it is larger than the sum of its proper divisors (1).

15661 is an equidigital number, since it uses as much as digits as its factorization.

15661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 180, while the sum is 19.

The square root of 15661 is about 125.1439171514. The cubic root of 15661 is about 25.0191852732.

Subtracting 15661 from its reverse (16651), we obtain a triangular number (990 = T44).

It can be divided in two parts, 15 and 661, that added together give a palindrome (676).

The spelling of 15661 in words is "fifteen thousand, six hundred sixty-one".