21558441 has 4 divisors (see below), whose sum is σ = 28744592. Its totient is φ = 14372292.

The previous prime is 21558413. The next prime is 21558443. The reversal of 21558441 is 14485512.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 21558441 - 2¹⁷ = 21427369 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21558399 and 21558408.

It is not an unprimeable number, because it can be changed into a prime (21558443) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3593071 + ... + 3593076.

It is an arithmetic number, because the mean of its divisors is an integer number (7186148).

Almost surely, 2^21558441 is an apocalyptic number.

It is an amenable number.

21558441 is a deficient number, since it is larger than the sum of its proper divisors (7186151).

21558441 is an equidigital number, since it uses as much as digits as its factorization.

21558441 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7186150.

The product of its digits is 6400, while the sum is 30.

The square root of 21558441 is about 4643.1068262533. The cubic root of 21558441 is about 278.3166044264.

The spelling of 21558441 in words is "twenty-one million, five hundred fifty-eight thousand, four hundred forty-one".