21634 has 8 divisors (see below), whose sum is σ = 33660. Its totient is φ = 10416.

The previous prime is 21617. The next prime is 21647. The reversal of 21634 is 43612.

21634 = T₁₀₂ + T₁₀₃ + ... + T₁₀₅.

21634 = 12² + 13² + ... + 40².

It can be written as a sum of positive squares in 2 ways, for example, as 21609 + 25 = 147^2 + 5^2 .

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 (5) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 129 + ... + 244.

2²¹⁶³⁴ is an apocalyptic number.

21634 is a deficient number, since it is larger than the sum of its proper divisors (12026).

21634 is a wasteful number, since it uses less digits than its factorization.

21634 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 404.

The product of its digits is 144, while the sum is 16.

The square root of 21634 is about 147.0850094333. The cubic root of 21634 is about 27.8641377507.

The spelling of 21634 in words is "twenty-one thousand, six hundred thirty-four".