21310212821 has 2 divisors, whose sum is σ = 21310212822. Its totient is φ = 21310212820.

The previous prime is 21310212817. The next prime is 21310212829. The reversal of 21310212821 is 12821201312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20629576900 + 680635921 = 143630^2 + 26089^2 .

It is a cyclic number.

It is not a de Polignac number, because 21310212821 - 2² = 21310212817 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21310212829) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10655106410 + 10655106411.

It is an arithmetic number, because the mean of its divisors is an integer number (10655106411).

Almost surely, 2^21310212821 is an apocalyptic number.

It is an amenable number.

21310212821 is a deficient number, since it is larger than the sum of its proper divisors (1).

21310212821 is an equidigital number, since it uses as much as digits as its factorization.

21310212821 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 384, while the sum is 23.

The spelling of 21310212821 in words is "twenty-one billion, three hundred ten million, two hundred twelve thousand, eight hundred twenty-one".