21389393 has 2 divisors, whose sum is σ = 21389394. Its totient is φ = 21389392.

The previous prime is 21389377. The next prime is 21389419. The reversal of 21389393 is 39398312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12909649 + 8479744 = 3593^2 + 2912^2 .

It is a cyclic number.

It is not a de Polignac number, because 21389393 - 2⁴ = 21389377 is a prime.

It is a super-2 number, since 2×21389393² = 915012265816898, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21389323) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10694696 + 10694697.

It is an arithmetic number, because the mean of its divisors is an integer number (10694697).

Almost surely, 2^21389393 is an apocalyptic number.

It is an amenable number.

21389393 is a deficient number, since it is larger than the sum of its proper divisors (1).

21389393 is an equidigital number, since it uses as much as digits as its factorization.

21389393 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 34992, while the sum is 38.

The square root of 21389393 is about 4624.8668088930. The cubic root of 21389393 is about 277.5872322677.

The spelling of 21389393 in words is "twenty-one million, three hundred eighty-nine thousand, three hundred ninety-three".