21581359 has 4 divisors (see below), whose sum is σ = 22717240. Its totient is φ = 20445480.

The previous prime is 21581353. The next prime is 21581369. The reversal of 21581359 is 95318512.

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 21581359 - 2⁵ = 21581327 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21581353) 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, 567912 + ... + 567949.

It is an arithmetic number, because the mean of its divisors is an integer number (5679310).

Almost surely, 2^21581359 is an apocalyptic number.

21581359 is a deficient number, since it is larger than the sum of its proper divisors (1135881).

21581359 is a wasteful number, since it uses less digits than its factorization.

21581359 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1135880.

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

The square root of 21581359 is about 4645.5741302879. The cubic root of 21581359 is about 278.4151922763.

The spelling of 21581359 in words is "twenty-one million, five hundred eighty-one thousand, three hundred fifty-nine".