21680069 has 2 divisors, whose sum is σ = 21680070. Its totient is φ = 21680068.

The previous prime is 21680059. The next prime is 21680077. The reversal of 21680069 is 96008612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21390625 + 289444 = 4625^2 + 538^2 .

It is a cyclic number.

It is not a de Polignac number, because 21680069 - 2⁸ = 21679813 is a prime.

It is a super-2 number, since 2×21680069² = 940050783689522, which contains 22 as substring.

It is a Sophie Germain 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 (21680059) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10840034 + 10840035.

It is an arithmetic number, because the mean of its divisors is an integer number (10840035).

Almost surely, 2^21680069 is an apocalyptic number.

It is an amenable number.

21680069 is a deficient number, since it is larger than the sum of its proper divisors (1).

21680069 is an equidigital number, since it uses as much as digits as its factorization.

21680069 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5184, while the sum is 32.

The square root of 21680069 is about 4656.1861002327. The cubic root of 21680069 is about 278.8390236279.

The spelling of 21680069 in words is "twenty-one million, six hundred eighty thousand, sixty-nine".