21216210631255 has 4 divisors (see below), whose sum is σ = 25459452757512. Its totient is φ = 16972968505000.

The previous prime is 21216210631249. The next prime is 21216210631289. The reversal of 21216210631255 is 55213601261212.

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

It is not a de Polignac number, because 21216210631255 - 2⁵ = 21216210631223 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, 2121621063121 + ... + 2121621063130.

It is an arithmetic number, because the mean of its divisors is an integer number (6364863189378).

Almost surely, 2^{21216210631255} is an apocalyptic number.

21216210631255 is a deficient number, since it is larger than the sum of its proper divisors (4243242126257).

21216210631255 is an equidigital number, since it uses as much as digits as its factorization.

21216210631255 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4243242126256.

The product of its (nonzero) digits is 43200, while the sum is 37.

Adding to 21216210631255 its reverse (55213601261212), we get a palindrome (76429811892467).

The spelling of 21216210631255 in words is "twenty-one trillion, two hundred sixteen billion, two hundred ten million, six hundred thirty-one thousand, two hundred fifty-five".