21641 has 8 divisors (see below), whose sum is σ = 24480. Its totient is φ = 19008.

The previous prime is 21617. The next prime is 21647. The reversal of 21641 is 14612.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21641 - 2⁶ = 21577 is a prime.

It is a Curzon number.

It is a nialpdrome in base 8.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21647) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 290 + ... + 356.

It is an arithmetic number, because the mean of its divisors is an integer number (3060).

2²¹⁶⁴¹ is an apocalyptic number.

It is an amenable number.

21641 is a deficient number, since it is larger than the sum of its proper divisors (2839).

21641 is a wasteful number, since it uses less digits than its factorization.

21641 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 103.

The product of its digits is 48, while the sum is 14.

The square root of 21641 is about 147.1088032716. The cubic root of 21641 is about 27.8671427109.

The spelling of 21641 in words is "twenty-one thousand, six hundred forty-one".