21704990389 has 2 divisors, whose sum is σ = 21704990390. Its totient is φ = 21704990388.

The previous prime is 21704990341. The next prime is 21704990401. The reversal of 21704990389 is 98309940712.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21675200625 + 29789764 = 147225^2 + 5458^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21704990389 is a prime.

It is a super-2 number, since 2×21704990389² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21704991389) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10852495194 + 10852495195.

It is an arithmetic number, because the mean of its divisors is an integer number (10852495195).

Almost surely, 2^21704990389 is an apocalyptic number.

It is an amenable number.

21704990389 is a deficient number, since it is larger than the sum of its proper divisors (1).

21704990389 is an equidigital number, since it uses as much as digits as its factorization.

21704990389 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 979776, while the sum is 52.

The spelling of 21704990389 in words is "twenty-one billion, seven hundred four million, nine hundred ninety thousand, three hundred eighty-nine".