21020099689 has 2 divisors, whose sum is σ = 21020099690. Its totient is φ = 21020099688.

The previous prime is 21020099687. The next prime is 21020099707. The reversal of 21020099689 is 98699002012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18367025625 + 2653074064 = 135525^2 + 51508^2 .

It is a cyclic number.

It is not a de Polignac number, because 21020099689 - 2¹ = 21020099687 is a prime.

Together with 21020099687, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21020099687) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10510049844 + 10510049845.

It is an arithmetic number, because the mean of its divisors is an integer number (10510049845).

Almost surely, 2^21020099689 is an apocalyptic number.

It is an amenable number.

21020099689 is a deficient number, since it is larger than the sum of its proper divisors (1).

21020099689 is an equidigital number, since it uses as much as digits as its factorization.

21020099689 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 139968, while the sum is 46.

The spelling of 21020099689 in words is "twenty-one billion, twenty million, ninety-nine thousand, six hundred eighty-nine".