21554434415 has 4 divisors (see below), whose sum is σ = 25865321304. Its totient is φ = 17243547528.

The previous prime is 21554434409. The next prime is 21554434417. The reversal of 21554434415 is 51443445512.

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 21554434415 - 2¹⁸ = 21554172271 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 (21554434417) 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, 2155443437 + ... + 2155443446.

It is an arithmetic number, because the mean of its divisors is an integer number (6466330326).

Almost surely, 2^21554434415 is an apocalyptic number.

21554434415 is a deficient number, since it is larger than the sum of its proper divisors (4310886889).

21554434415 is an equidigital number, since it uses as much as digits as its factorization.

21554434415 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4310886888.

The product of its digits is 192000, while the sum is 38.

Adding to 21554434415 its reverse (51443445512), we get a palindrome (72997879927).

The spelling of 21554434415 in words is "twenty-one billion, five hundred fifty-four million, four hundred thirty-four thousand, four hundred fifteen".