15664210021 has 2 divisors, whose sum is σ = 15664210022. Its totient is φ = 15664210020.

The previous prime is 15664210013. The next prime is 15664210087. The reversal of 15664210021 is 12001246651.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14930396100 + 733813921 = 122190^2 + 27089^2 .

It is an emirp because it is prime and its reverse (12001246651) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 15664210021 - 2³ = 15664210013 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (15664210621) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7832105010 + 7832105011.

It is an arithmetic number, because the mean of its divisors is an integer number (7832105011).

Almost surely, 2^15664210021 is an apocalyptic number.

It is an amenable number.

15664210021 is a deficient number, since it is larger than the sum of its proper divisors (1).

15664210021 is an equidigital number, since it uses as much as digits as its factorization.

15664210021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2880, while the sum is 28.

Adding to 15664210021 its reverse (12001246651), we get a palindrome (27665456672).

The spelling of 15664210021 in words is "fifteen billion, six hundred sixty-four million, two hundred ten thousand, twenty-one".