21553541 has 4 divisors (see below), whose sum is σ = 21857184. Its totient is φ = 21249900.

The previous prime is 21553531. The next prime is 21553613. The reversal of 21553541 is 14535512.

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 21553541 - 2¹⁸ = 21291397 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21553541.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21553531) 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, 151715 + ... + 151856.

It is an arithmetic number, because the mean of its divisors is an integer number (5464296).

Almost surely, 2^21553541 is an apocalyptic number.

It is an amenable number.

21553541 is a deficient number, since it is larger than the sum of its proper divisors (303643).

21553541 is an equidigital number, since it uses as much as digits as its factorization.

21553541 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 303642.

The product of its digits is 3000, while the sum is 26.

The square root of 21553541 is about 4642.5791323358. The cubic root of 21553541 is about 278.2955167127.

The spelling of 21553541 in words is "twenty-one million, five hundred fifty-three thousand, five hundred forty-one".