21619 has 4 divisors (see below), whose sum is σ = 23296. Its totient is φ = 19944.

The previous prime is 21617. The next prime is 21647. The reversal of 21619 is 91612.

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

It is a cyclic number.

It is not a de Polignac number, because 21619 - 2¹ = 21617 is a prime.

It is a super-2 number, since 2×21619² = 934762322, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21596 and 21605.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21611) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 819 + ... + 844.

It is an arithmetic number, because the mean of its divisors is an integer number (5824).

2²¹⁶¹⁹ is an apocalyptic number.

21619 is a deficient number, since it is larger than the sum of its proper divisors (1677).

21619 is a wasteful number, since it uses less digits than its factorization.

21619 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1676.

The product of its digits is 108, while the sum is 19.

The square root of 21619 is about 147.0340096712. The cubic root of 21619 is about 27.8576963667.

The spelling of 21619 in words is "twenty-one thousand, six hundred nineteen".