21365554706409 has 4 divisors (see below), whose sum is σ = 28487406275216. Its totient is φ = 14243703137604.

The previous prime is 21365554706401. The next prime is 21365554706411. The reversal of 21365554706409 is 90460745556312.

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 21365554706409 - 2³ = 21365554706401 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21365554706401) 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, 3560925784399 + ... + 3560925784404.

It is an arithmetic number, because the mean of its divisors is an integer number (7121851568804).

Almost surely, 2^{21365554706409} is an apocalyptic number.

It is an amenable number.

21365554706409 is a deficient number, since it is larger than the sum of its proper divisors (7121851568807).

21365554706409 is an equidigital number, since it uses as much as digits as its factorization.

21365554706409 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7121851568806.

The product of its (nonzero) digits is 27216000, while the sum is 57.

The spelling of 21365554706409 in words is "twenty-one trillion, three hundred sixty-five billion, five hundred fifty-four million, seven hundred six thousand, four hundred nine".