21208969 has 2 divisors, whose sum is σ = 21208970. Its totient is φ = 21208968.

The previous prime is 21208961. The next prime is 21208981. The reversal of 21208969 is 96980212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17749369 + 3459600 = 4213^2 + 1860^2 .

It is a cyclic number.

It is not a de Polignac number, because 21208969 - 2³ = 21208961 is a prime.

It is a super-2 number, since 2×21208969² = 899640732085922, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21208961) 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, 10604484 + 10604485.

It is an arithmetic number, because the mean of its divisors is an integer number (10604485).

Almost surely, 2^21208969 is an apocalyptic number.

It is an amenable number.

21208969 is a deficient number, since it is larger than the sum of its proper divisors (1).

21208969 is an equidigital number, since it uses as much as digits as its factorization.

21208969 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 15552, while the sum is 37.

The square root of 21208969 is about 4605.3196414581. The cubic root of 21208969 is about 276.8045252540.

The spelling of 21208969 in words is "twenty-one million, two hundred eight thousand, nine hundred sixty-nine".