21290 has 8 divisors (see below), whose sum is σ = 38340. Its totient is φ = 8512.

The previous prime is 21283. The next prime is 21313. The reversal of 21290 is 9212.

It can be written as a sum of positive squares in 2 ways, for example, as 20449 + 841 = 143^2 + 29^2 .

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

It is an alternating number because its digits alternate between even and odd.

It is an unprimeable number.

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, 1055 + ... + 1074.

2²¹²⁹⁰ is an apocalyptic number.

21290 is a deficient number, since it is larger than the sum of its proper divisors (17050).

21290 is a wasteful number, since it uses less digits than its factorization.

21290 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2136.

The product of its (nonzero) digits is 36, while the sum is 14.

The square root of 21290 is about 145.9109317358. The cubic root of 21290 is about 27.7156597105.

The spelling of 21290 in words is "twenty-one thousand, two hundred ninety".