21558641 has 8 divisors (see below), whose sum is σ = 23313024. Its totient is φ = 19818000.

The previous prime is 21558619. The next prime is 21558643. The reversal of 21558641 is 14685512.

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 21558641 - 2⁶ = 21558577 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21558598 and 21558607.

It is not an unprimeable number, because it can be changed into a prime (21558643) 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 7 ways as a sum of consecutive naturals, for example, 41 + ... + 6566.

It is an arithmetic number, because the mean of its divisors is an integer number (2914128).

Almost surely, 2^21558641 is an apocalyptic number.

It is an amenable number.

21558641 is a deficient number, since it is larger than the sum of its proper divisors (1754383).

21558641 is a wasteful number, since it uses less digits than its factorization.

21558641 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6871.

The product of its digits is 9600, while the sum is 32.

The square root of 21558641 is about 4643.1283635067. The cubic root of 21558641 is about 278.3174650815.

The spelling of 21558641 in words is "twenty-one million, five hundred fifty-eight thousand, six hundred forty-one".