21555241 has 4 divisors (see below), whose sum is σ = 21577984. Its totient is φ = 21532500.

The previous prime is 21555223. The next prime is 21555263. The reversal of 21555241 is 14255512.

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 a cyclic number.

It is not a de Polignac number, because 21555241 - 2⁷ = 21555113 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21555211) 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, 9885 + ... + 11866.

It is an arithmetic number, because the mean of its divisors is an integer number (5394496).

Almost surely, 2^21555241 is an apocalyptic number.

21555241 is the 2681-st hex number.

It is an amenable number.

21555241 is a deficient number, since it is larger than the sum of its proper divisors (22743).

21555241 is an equidigital number, since it uses as much as digits as its factorization.

21555241 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22742.

The product of its digits is 2000, while the sum is 25.

The square root of 21555241 is about 4642.7622166120. The cubic root of 21555241 is about 278.3028332203.

It can be divided in two parts, 2155 and 5241, that added together give a square (7396 = 86²).

The spelling of 21555241 in words is "twenty-one million, five hundred fifty-five thousand, two hundred forty-one".