21216305797 has 2 divisors, whose sum is σ = 21216305798. Its totient is φ = 21216305796.

The previous prime is 21216305741. The next prime is 21216305833. The reversal of 21216305797 is 79750361212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19194994116 + 2021311681 = 138546^2 + 44959^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21216305797 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21216305197) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10608152898 + 10608152899.

It is an arithmetic number, because the mean of its divisors is an integer number (10608152899).

Almost surely, 2^21216305797 is an apocalyptic number.

It is an amenable number.

21216305797 is a deficient number, since it is larger than the sum of its proper divisors (1).

21216305797 is an equidigital number, since it uses as much as digits as its factorization.

21216305797 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 158760, while the sum is 43.

The spelling of 21216305797 in words is "twenty-one billion, two hundred sixteen million, three hundred five thousand, seven hundred ninety-seven".