21989389 has 2 divisors, whose sum is σ = 21989390. Its totient is φ = 21989388.

The previous prime is 21989377. The next prime is 21989399. The reversal of 21989389 is 98398912.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12638025 + 9351364 = 3555^2 + 3058^2 .

It is a cyclic number.

It is not a de Polignac number, because 21989389 - 2¹⁵ = 21956621 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21989369) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10994694 + 10994695.

It is an arithmetic number, because the mean of its divisors is an integer number (10994695).

Almost surely, 2^21989389 is an apocalyptic number.

It is an amenable number.

21989389 is a deficient number, since it is larger than the sum of its proper divisors (1).

21989389 is an equidigital number, since it uses as much as digits as its factorization.

21989389 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 279936, while the sum is 49.

The square root of 21989389 is about 4689.2844869980. The cubic root of 21989389 is about 280.1588766704.

The spelling of 21989389 in words is "twenty-one million, nine hundred eighty-nine thousand, three hundred eighty-nine".