21049 has 8 divisors (see below), whose sum is σ = 25088. Its totient is φ = 17280.

The previous prime is 21031. The next prime is 21059. The reversal of 21049 is 94012.

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 21049 - 2⁵ = 21017 is a prime.

It is an Ulam number.

21049 is a lucky number.

It is a nialpdrome in base 13.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21019) 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 7 ways as a sum of consecutive naturals, for example, 169 + ... + 265.

It is an arithmetic number, because the mean of its divisors is an integer number (3136).

2²¹⁰⁴⁹ is an apocalyptic number.

It is an amenable number.

21049 is a deficient number, since it is larger than the sum of its proper divisors (4039).

21049 is an equidigital number, since it uses as much as digits as its factorization.

21049 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 135.

The product of its (nonzero) digits is 72, while the sum is 16.

The square root of 21049 is about 145.0827350170. The cubic root of 21049 is about 27.6106833948.

The spelling of 21049 in words is "twenty-one thousand, forty-nine".