21002789 has 2 divisors, whose sum is σ = 21002790. Its totient is φ = 21002788.

The previous prime is 21002777. The next prime is 21002797. The reversal of 21002789 is 98720012.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19070689 + 1932100 = 4367^2 + 1390^2 .

It is a cyclic number.

It is not a de Polignac number, because 21002789 - 2¹⁶ = 20937253 is a prime.

It is a super-2 number, since 2×21002789² = 882234291557042, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21002389) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10501394 + 10501395.

It is an arithmetic number, because the mean of its divisors is an integer number (10501395).

Almost surely, 2^21002789 is an apocalyptic number.

It is an amenable number.

21002789 is a deficient number, since it is larger than the sum of its proper divisors (1).

21002789 is an equidigital number, since it uses as much as digits as its factorization.

21002789 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2016, while the sum is 29.

The square root of 21002789 is about 4582.8799897008. The cubic root of 21002789 is about 275.9046308110.

The spelling of 21002789 in words is "twenty-one million, two thousand, seven hundred eighty-nine".