21164989 has 2 divisors, whose sum is σ = 21164990. Its totient is φ = 21164988.

The previous prime is 21164953. The next prime is 21165007. The reversal of 21164989 is 98946112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14100025 + 7064964 = 3755^2 + 2658^2 .

It is a cyclic number.

It is not a de Polignac number, because 21164989 - 2⁹ = 21164477 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21164929) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10582494 + 10582495.

It is an arithmetic number, because the mean of its divisors is an integer number (10582495).

Almost surely, 2^21164989 is an apocalyptic number.

It is an amenable number.

21164989 is a deficient number, since it is larger than the sum of its proper divisors (1).

21164989 is an equidigital number, since it uses as much as digits as its factorization.

21164989 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 31104, while the sum is 40.

The square root of 21164989 is about 4600.5422506483. The cubic root of 21164989 is about 276.6130608550.

The spelling of 21164989 in words is "twenty-one million, one hundred sixty-four thousand, nine hundred eighty-nine".