21085904393 has 2 divisors, whose sum is σ = 21085904394. Its totient is φ = 21085904392.

The previous prime is 21085904381. The next prime is 21085904461. The reversal of 21085904393 is 39340958012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 10883288329 + 10202616064 = 104323^2 + 101008^2 .

It is a cyclic number.

It is not a de Polignac number, because 21085904393 - 2¹⁶ = 21085838857 is a prime.

It is not a weakly prime, because it can be changed into another prime (21085904093) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10542952196 + 10542952197.

It is an arithmetic number, because the mean of its divisors is an integer number (10542952197).

Almost surely, 2^21085904393 is an apocalyptic number.

It is an amenable number.

21085904393 is a deficient number, since it is larger than the sum of its proper divisors (1).

21085904393 is an equidigital number, since it uses as much as digits as its factorization.

21085904393 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 233280, while the sum is 44.

The spelling of 21085904393 in words is "twenty-one billion, eighty-five million, nine hundred four thousand, three hundred ninety-three".