21164789 has 2 divisors, whose sum is σ = 21164790. Its totient is φ = 21164788.

The previous prime is 21164771. The next prime is 21164797. The reversal of 21164789 is 98746112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15665764 + 5499025 = 3958^2 + 2345^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21164789 is a prime.

It is a super-3 number, since 3×21164789³ (a number of 23 digits) contains 333 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21164189) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10582394 + 10582395.

It is an arithmetic number, because the mean of its divisors is an integer number (10582395).

Almost surely, 2^21164789 is an apocalyptic number.

It is an amenable number.

21164789 is a deficient number, since it is larger than the sum of its proper divisors (1).

21164789 is an equidigital number, since it uses as much as digits as its factorization.

21164789 is an evil number, because the sum of its binary digits is even.

The product of its digits is 24192, while the sum is 38.

The square root of 21164789 is about 4600.5205140288. The cubic root of 21164789 is about 276.6121895610.

The spelling of 21164789 in words is "twenty-one million, one hundred sixty-four thousand, seven hundred eighty-nine".