16621 has 4 divisors (see below), whose sum is σ = 18144.
Its totient is φ = 15100.
The previous prime is 16619. The next prime is 16631. The reversal of 16621 is 12661.
It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 12661 = 11 ⋅1151.
It is a cyclic number.
It is not a de Polignac number, because 16621 - 21 = 16619 is a prime.
It is a Duffinian number.
16621 is a lucky number.
It is a nialpdrome in base 12.
It is a junction number, because it is equal to n+sod(n) for n = 16595 and 16604.
It is a congruent number.
It is not an unprimeable number, because it can be changed into a prime (16631) by changing a digit.
It is a pernicious number, because its binary representation contains a prime number (7) of ones.
It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 745 + ... + 766.
It is an arithmetic number, because the mean of its divisors is an integer number (4536).
216621 is an apocalyptic number.
16621 is a gapful number since it is divisible by the number (11) formed by its first and last digit.
It is an amenable number.
16621 is a deficient number, since it is larger than the sum of its proper divisors (1523).
16621 is a wasteful number, since it uses less digits than its factorization.
16621 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 1522.
The product of its digits is 72, while the sum is 16.
The square root of 16621 is about 128.9224573145.
The cubic root of 16621 is about 25.5202965411.
It can be divided in two parts, 166 and 21, that multiplied together give a triangular number (3486 = T83).
The spelling of 16621 in words is "sixteen thousand, six hundred twenty-one".