21213556440205 has 4 divisors (see below), whose sum is σ = 25456267728252. Its totient is φ = 16970845152160.

The previous prime is 21213556440199. The next prime is 21213556440221. The reversal of 21213556440205 is 50204465531212.

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 8724810380841 + 12488746059364 = 2953779^2 + 3533942^2 .

It is not a de Polignac number, because 21213556440205 - 2²⁵ = 21213522885773 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, 2121355644016 + ... + 2121355644025.

It is an arithmetic number, because the mean of its divisors is an integer number (6364066932063).

Almost surely, 2^{21213556440205} is an apocalyptic number.

It is an amenable number.

21213556440205 is a deficient number, since it is larger than the sum of its proper divisors (4242711288047).

21213556440205 is an equidigital number, since it uses as much as digits as its factorization.

21213556440205 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4242711288046.

The product of its (nonzero) digits is 288000, while the sum is 40.

The spelling of 21213556440205 in words is "twenty-one trillion, two hundred thirteen billion, five hundred fifty-six million, four hundred forty thousand, two hundred five".