21021631668689 has 2 divisors, whose sum is σ = 21021631668690. Its totient is φ = 21021631668688.

The previous prime is 21021631668683. The next prime is 21021631668701. The reversal of 21021631668689 is 98686613612012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13315638883600 + 7705992785089 = 3649060^2 + 2775967^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21021631668689 is a prime.

It is not a weakly prime, because it can be changed into another prime (21021631668683) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10510815834344 + 10510815834345.

It is an arithmetic number, because the mean of its divisors is an integer number (10510815834345).

Almost surely, 2^{21021631668689} is an apocalyptic number.

It is an amenable number.

21021631668689 is a deficient number, since it is larger than the sum of its proper divisors (1).

21021631668689 is an equidigital number, since it uses as much as digits as its factorization.

21021631668689 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 8957952, while the sum is 59.

The spelling of 21021631668689 in words is "twenty-one trillion, twenty-one billion, six hundred thirty-one million, six hundred sixty-eight thousand, six hundred eighty-nine".