21216042050251 has 4 divisors (see below), whose sum is σ = 21216056017312. Its totient is φ = 21216028083192.

The previous prime is 21216042050243. The next prime is 21216042050297. The reversal of 21216042050251 is 15205024061212.

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 21216042050251 - 2³ = 21216042050243 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21216042090251) 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, 4381971 + ... + 7850716.

It is an arithmetic number, because the mean of its divisors is an integer number (5304014004328).

Almost surely, 2^{21216042050251} is an apocalyptic number.

21216042050251 is a deficient number, since it is larger than the sum of its proper divisors (13967061).

21216042050251 is a wasteful number, since it uses less digits than its factorization.

21216042050251 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13967060.

The product of its (nonzero) digits is 9600, while the sum is 31.

The spelling of 21216042050251 in words is "twenty-one trillion, two hundred sixteen billion, forty-two million, fifty thousand, two hundred fifty-one".