16651 has 2 divisors, whose sum is σ = 16652. Its totient is φ = 16650.

The previous prime is 16649. The next prime is 16657. The reversal of 16651 is 15661.

16651 is nontrivially palindromic in base 5.

It is a weak prime.

It is an emirp because it is prime and its reverse (15661) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 16651 - 2¹ = 16649 is a prime.

Together with 16649, it forms a pair of twin primes.

It is an Ulam number.

It is a plaindrome in base 11.

It is a nialpdrome in base 12.

It is not a weakly prime, because it can be changed into another prime (16657) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8325 + 8326.

It is an arithmetic number, because the mean of its divisors is an integer number (8326).

2¹⁶⁶⁵¹ is an apocalyptic number.

16651 is the 75-th hex number.

16651 is a deficient number, since it is larger than the sum of its proper divisors (1).

16651 is an equidigital number, since it uses as much as digits as its factorization.

16651 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 16651 is about 129.0387538688. The cubic root of 16651 is about 25.5356415610.

Subtracting from 16651 its product of digits (180), we obtain a triangular number (16471 = T₁₈₁).

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

The spelling of 16651 in words is "sixteen thousand, six hundred fifty-one".