21675869 has 2 divisors, whose sum is σ = 21675870. Its totient is φ = 21675868.

The previous prime is 21675853. The next prime is 21675877. The reversal of 21675869 is 96857612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13410244 + 8265625 = 3662^2 + 2875^2 .

It is a cyclic number.

It is not a de Polignac number, because 21675869 - 2⁴ = 21675853 is a prime.

It is a super-2 number, since 2×21675869² = 939686593810322, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21675809) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10837934 + 10837935.

It is an arithmetic number, because the mean of its divisors is an integer number (10837935).

Almost surely, 2^21675869 is an apocalyptic number.

It is an amenable number.

21675869 is a deficient number, since it is larger than the sum of its proper divisors (1).

21675869 is an equidigital number, since it uses as much as digits as its factorization.

21675869 is an evil number, because the sum of its binary digits is even.

The product of its digits is 181440, while the sum is 44.

The square root of 21675869 is about 4655.7350654864. The cubic root of 21675869 is about 278.8210163123.

The spelling of 21675869 in words is "twenty-one million, six hundred seventy-five thousand, eight hundred sixty-nine".