21216523501 has 2 divisors, whose sum is σ = 21216523502. Its totient is φ = 21216523500.

The previous prime is 21216523483. The next prime is 21216523513. The reversal of 21216523501 is 10532561212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20542342276 + 674181225 = 143326^2 + 25965^2 .

It is a cyclic number.

It is not a de Polignac number, because 21216523501 - 2⁵ = 21216523469 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21216523501.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21216523541) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10608261750 + 10608261751.

It is an arithmetic number, because the mean of its divisors is an integer number (10608261751).

Almost surely, 2^21216523501 is an apocalyptic number.

It is an amenable number.

21216523501 is a deficient number, since it is larger than the sum of its proper divisors (1).

21216523501 is an equidigital number, since it uses as much as digits as its factorization.

21216523501 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3600, while the sum is 28.

The spelling of 21216523501 in words is "twenty-one billion, two hundred sixteen million, five hundred twenty-three thousand, five hundred one".