21003869 has 2 divisors, whose sum is σ = 21003870. Its totient is φ = 21003868.

The previous prime is 21003821. The next prime is 21003883. The reversal of 21003869 is 96830012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18164644 + 2839225 = 4262^2 + 1685^2 .

It is a cyclic number.

It is not a de Polignac number, because 21003869 - 2²⁰ = 19955293 is a prime.

It is a super-2 number, since 2×21003869² = 882325025938322, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21009869) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10501934 + 10501935.

It is an arithmetic number, because the mean of its divisors is an integer number (10501935).

Almost surely, 2^21003869 is an apocalyptic number.

It is an amenable number.

21003869 is a deficient number, since it is larger than the sum of its proper divisors (1).

21003869 is an equidigital number, since it uses as much as digits as its factorization.

21003869 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2592, while the sum is 29.

The square root of 21003869 is about 4582.9978180226. The cubic root of 21003869 is about 275.9093598955.

The spelling of 21003869 in words is "twenty-one million, three thousand, eight hundred sixty-nine".