21554321 has 4 divisors (see below), whose sum is σ = 21609012. Its totient is φ = 21499632.

The previous prime is 21554311. The next prime is 21554359. The reversal of 21554321 is 12345512.

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

It can be written as a sum of positive squares in 2 ways, for example, as 19492225 + 2062096 = 4415^2 + 1436^2 .

It is a cyclic number.

It is not a de Polignac number, because 21554321 - 2⁶ = 21554257 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21554311) 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, 26750 + ... + 27543.

It is an arithmetic number, because the mean of its divisors is an integer number (5402253).

Almost surely, 2^21554321 is an apocalyptic number.

It is an amenable number.

21554321 is a deficient number, since it is larger than the sum of its proper divisors (54691).

21554321 is an equidigital number, since it uses as much as digits as its factorization.

21554321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 54690.

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

The square root of 21554321 is about 4642.6631366060. The cubic root of 21554321 is about 278.2988737463.

Adding to 21554321 its reverse (12345512), we get a palindrome (33899833).

The spelling of 21554321 in words is "twenty-one million, five hundred fifty-four thousand, three hundred twenty-one".