21216360421 has 2 divisors, whose sum is σ = 21216360422. Its totient is φ = 21216360420.

The previous prime is 21216360401. The next prime is 21216360449. The reversal of 21216360421 is 12406361212.

It is an a-pointer prime, because the next prime (21216360449) can be obtained adding 21216360421 to its sum of digits (28).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20689657921 + 526702500 = 143839^2 + 22950^2 .

It is a cyclic number.

It is not a de Polignac number, because 21216360421 - 2²⁵ = 21182805989 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21216360421.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21216360401) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10608180210 + 10608180211.

It is an arithmetic number, because the mean of its divisors is an integer number (10608180211).

Almost surely, 2^21216360421 is an apocalyptic number.

It is an amenable number.

21216360421 is a deficient number, since it is larger than the sum of its proper divisors (1).

21216360421 is an equidigital number, since it uses as much as digits as its factorization.

21216360421 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3456, while the sum is 28.

The spelling of 21216360421 in words is "twenty-one billion, two hundred sixteen million, three hundred sixty thousand, four hundred twenty-one".