21161869 has 2 divisors, whose sum is σ = 21161870. Its totient is φ = 21161868.

The previous prime is 21161867. The next prime is 21161887. The reversal of 21161869 is 96816112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19096900 + 2064969 = 4370^2 + 1437^2 .

It is a cyclic number.

It is not a de Polignac number, because 21161869 - 2¹ = 21161867 is a prime.

It is a super-2 number, since 2×21161869² = 895649399146322, which contains 22 as substring.

Together with 21161867, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21161867) 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, 10580934 + 10580935.

It is an arithmetic number, because the mean of its divisors is an integer number (10580935).

Almost surely, 2^21161869 is an apocalyptic number.

It is an amenable number.

21161869 is a deficient number, since it is larger than the sum of its proper divisors (1).

21161869 is an equidigital number, since it uses as much as digits as its factorization.

21161869 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5184, while the sum is 34.

The square root of 21161869 is about 4600.2031476882. The cubic root of 21161869 is about 276.5994680428.

The spelling of 21161869 in words is "twenty-one million, one hundred sixty-one thousand, eight hundred sixty-nine".