21553471 has 4 divisors (see below), whose sum is σ = 21762832. Its totient is φ = 21344112.

The previous prime is 21553459. The next prime is 21553481. The reversal of 21553471 is 17435512.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21553471 - 2¹¹ = 21551423 is a prime.

It is a super-3 number, since 3×21553471³ (a number of 23 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21553421) 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 3 ways as a sum of consecutive naturals, for example, 104526 + ... + 104731.

It is an arithmetic number, because the mean of its divisors is an integer number (5440708).

Almost surely, 2^21553471 is an apocalyptic number.

21553471 is a deficient number, since it is larger than the sum of its proper divisors (209361).

21553471 is a wasteful number, since it uses less digits than its factorization.

21553471 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 209360.

The product of its digits is 4200, while the sum is 28.

The square root of 21553471 is about 4642.5715934167. The cubic root of 21553471 is about 278.2952154365.

Adding to 21553471 its reverse (17435512), we get a palindrome (38988983).

The spelling of 21553471 in words is "twenty-one million, five hundred fifty-three thousand, four hundred seventy-one".