21859531 has 4 divisors (see below), whose sum is σ = 22076064. Its totient is φ = 21643000.

The previous prime is 21859529. The next prime is 21859543. The reversal of 21859531 is 13595812.

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 21859531 - 2¹ = 21859529 is a prime.

It is a super-2 number, since 2×21859531² = 955678191079922, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21859561) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 108115 + ... + 108316.

It is an arithmetic number, because the mean of its divisors is an integer number (5519016).

Almost surely, 2^21859531 is an apocalyptic number.

21859531 is a deficient number, since it is larger than the sum of its proper divisors (216533).

21859531 is a wasteful number, since it uses less digits than its factorization.

21859531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 216532.

The product of its digits is 10800, while the sum is 34.

The square root of 21859531 is about 4675.4177353473. The cubic root of 21859531 is about 279.6062961682.

The spelling of 21859531 in words is "twenty-one million, eight hundred fifty-nine thousand, five hundred thirty-one".