21551353221 has 8 divisors (see below), whose sum is σ = 28737016960. Its totient is φ = 14366629152.

The previous prime is 21551353189. The next prime is 21551353289. The reversal of 21551353221 is 12235315512.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21551353221 - 2⁵ = 21551353189 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21551353721) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 179536 + ... + 274473.

It is an arithmetic number, because the mean of its divisors is an integer number (3592127120).

Almost surely, 2^21551353221 is an apocalyptic number.

It is an amenable number.

21551353221 is a deficient number, since it is larger than the sum of its proper divisors (7185663739).

21551353221 is a wasteful number, since it uses less digits than its factorization.

21551353221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 469835.

The product of its digits is 9000, while the sum is 30.

Adding to 21551353221 its reverse (12235315512), we get a palindrome (33786668733).

The spelling of 21551353221 in words is "twenty-one billion, five hundred fifty-one million, three hundred fifty-three thousand, two hundred twenty-one".