21553241 has 4 divisors (see below), whose sum is σ = 21562752. Its totient is φ = 21543732.

The previous prime is 21553223. The next prime is 21553243. The reversal of 21553241 is 14235512.

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, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21553241 - 2¹⁸ = 21291097 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21553243) 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, 836 + ... + 6618.

It is an arithmetic number, because the mean of its divisors is an integer number (5390688).

Almost surely, 2^21553241 is an apocalyptic number.

It is an amenable number.

21553241 is a deficient number, since it is larger than the sum of its proper divisors (9511).

21553241 is an equidigital number, since it uses as much as digits as its factorization.

21553241 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9510.

The product of its digits is 1200, while the sum is 23.

The square root of 21553241 is about 4642.5468225964. The cubic root of 21553241 is about 278.2942255243.

Adding to 21553241 its reverse (14235512), we get a palindrome (35788753).

The spelling of 21553241 in words is "twenty-one million, five hundred fifty-three thousand, two hundred forty-one".