21002389 has 2 divisors, whose sum is σ = 21002390. Its totient is φ = 21002388.

The previous prime is 21002357. The next prime is 21002393. The reversal of 21002389 is 98320012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14190289 + 6812100 = 3767^2 + 2610^2 .

It is a cyclic number.

It is not a de Polignac number, because 21002389 - 2⁵ = 21002357 is a prime.

It is a super-2 number, since 2×21002389² = 882200687414642, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21002329) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10501194 + 10501195.

It is an arithmetic number, because the mean of its divisors is an integer number (10501195).

Almost surely, 2^21002389 is an apocalyptic number.

It is an amenable number.

21002389 is a deficient number, since it is larger than the sum of its proper divisors (1).

21002389 is an equidigital number, since it uses as much as digits as its factorization.

21002389 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 864, while the sum is 25.

The square root of 21002389 is about 4582.8363488128. The cubic root of 21002389 is about 275.9028792571.

It can be divided in two parts, 2100 and 2389, that added together give a square (4489 = 67²).

The spelling of 21002389 in words is "twenty-one million, two thousand, three hundred eighty-nine".