21561859 has 8 divisors (see below), whose sum is σ = 24096240. Its totient is φ = 19123200.

The previous prime is 21561851. The next prime is 21561887. The reversal of 21561859 is 95816512.

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 21561859 - 2³ = 21561851 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21561851) 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, 23454 + ... + 24355.

It is an arithmetic number, because the mean of its divisors is an integer number (3012030).

Almost surely, 2^21561859 is an apocalyptic number.

21561859 is a deficient number, since it is larger than the sum of its proper divisors (2534381).

21561859 is a wasteful number, since it uses less digits than its factorization.

21561859 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 47861.

The product of its digits is 21600, while the sum is 37.

The square root of 21561859 is about 4643.4748841789. The cubic root of 21561859 is about 278.3313122909.

It can be divided in two parts, 2156 and 1859, that multiplied together give a palindrome (4008004).

The spelling of 21561859 in words is "twenty-one million, five hundred sixty-one thousand, eight hundred fifty-nine".