21211553 has 4 divisors (see below), whose sum is σ = 23139888. Its totient is φ = 19283220.

The previous prime is 21211507. The next prime is 21211577. The reversal of 21211553 is 35511212.

It is a happy number.

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 21211553 - 2¹⁰ = 21210529 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21213553) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 964151 + ... + 964172.

It is an arithmetic number, because the mean of its divisors is an integer number (5784972).

Almost surely, 2^21211553 is an apocalyptic number.

It is an amenable number.

21211553 is a deficient number, since it is larger than the sum of its proper divisors (1928335).

21211553 is a wasteful number, since it uses less digits than its factorization.

21211553 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1928334.

The product of its digits is 300, while the sum is 20.

The square root of 21211553 is about 4605.6001780441. The cubic root of 21211553 is about 276.8157663135.

Adding to 21211553 its reverse (35511212), we get a palindrome (56722765).

The spelling of 21211553 in words is "twenty-one million, two hundred eleven thousand, five hundred fifty-three".