21019869 has 12 divisors (see below), whose sum is σ = 32697756. Its totient is φ = 12935232.

The previous prime is 21019849. The next prime is 21019879. The reversal of 21019869 is 96891012.

It can be written as a sum of positive squares in 2 ways, for example, as 11471769 + 9548100 = 3387^2 + 3090^2 .

It is not a de Polignac number, because 21019869 - 2⁸ = 21019613 is a prime.

It is a super-2 number, since 2×21019869² = 883669785554322, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21019849) 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 in 11 ways as a sum of consecutive naturals, for example, 89712 + ... + 89945.

It is an arithmetic number, because the mean of its divisors is an integer number (2724813).

Almost surely, 2^21019869 is an apocalyptic number.

It is an amenable number.

21019869 is a deficient number, since it is larger than the sum of its proper divisors (11677887).

21019869 is a wasteful number, since it uses less digits than its factorization.

21019869 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 179676 (or 179673 counting only the distinct ones).

The product of its (nonzero) digits is 7776, while the sum is 36.

The square root of 21019869 is about 4584.7430680465. The cubic root of 21019869 is about 275.9794014243.

The spelling of 21019869 in words is "twenty-one million, nineteen thousand, eight hundred sixty-nine".