21554321405 has 4 divisors (see below), whose sum is σ = 25865185692. Its totient is φ = 17243457120.

The previous prime is 21554321387. The next prime is 21554321417. The reversal of 21554321405 is 50412345512.

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 7083915556 + 14470405849 = 84166^2 + 120293^2 .

It is not a de Polignac number, because 21554321405 - 2⁸ = 21554321149 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2155432136 + ... + 2155432145.

It is an arithmetic number, because the mean of its divisors is an integer number (6466296423).

Almost surely, 2^21554321405 is an apocalyptic number.

It is an amenable number.

21554321405 is a deficient number, since it is larger than the sum of its proper divisors (4310864287).

21554321405 is an equidigital number, since it uses as much as digits as its factorization.

21554321405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4310864286.

The product of its (nonzero) digits is 24000, while the sum is 32.

Adding to 21554321405 its reverse (50412345512), we get a palindrome (71966666917).

The spelling of 21554321405 in words is "twenty-one billion, five hundred fifty-four million, three hundred twenty-one thousand, four hundred five".