21819869 has 2 divisors, whose sum is σ = 21819870. Its totient is φ = 21819868.

The previous prime is 21819841. The next prime is 21819871. The reversal of 21819869 is 96891812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16297369 + 5522500 = 4037^2 + 2350^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21819869 is a prime.

It is a super-2 number, since 2×21819869² = 952213366354322, which contains 22 as substring.

Together with 21819871, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21819169) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10909934 + 10909935.

It is an arithmetic number, because the mean of its divisors is an integer number (10909935).

Almost surely, 2^21819869 is an apocalyptic number.

It is an amenable number.

21819869 is a deficient number, since it is larger than the sum of its proper divisors (1).

21819869 is an equidigital number, since it uses as much as digits as its factorization.

21819869 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 62208, while the sum is 44.

The square root of 21819869 is about 4671.1742635016. The cubic root of 21819869 is about 279.4370876160.

The spelling of 21819869 in words is "twenty-one million, eight hundred nineteen thousand, eight hundred sixty-nine".