21859021 has 4 divisors (see below), whose sum is σ = 21876444. Its totient is φ = 21841600.

The previous prime is 21859009. The next prime is 21859031. The reversal of 21859021 is 12095812.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1473796 + 20385225 = 1214^2 + 4515^2 .

It is a cyclic number.

It is not a de Polignac number, because 21859021 - 2⁵ = 21858989 is a prime.

It is a super-3 number, since 3×21859021³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21859031) 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, 6670 + ... + 9391.

It is an arithmetic number, because the mean of its divisors is an integer number (5469111).

Almost surely, 2^21859021 is an apocalyptic number.

It is an amenable number.

21859021 is a deficient number, since it is larger than the sum of its proper divisors (17423).

21859021 is a wasteful number, since it uses less digits than its factorization.

21859021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17422.

The product of its (nonzero) digits is 1440, while the sum is 28.

The square root of 21859021 is about 4675.3631944481. The cubic root of 21859021 is about 279.6041216732.

The spelling of 21859021 in words is "twenty-one million, eight hundred fifty-nine thousand, twenty-one".