21680497 has 2 divisors, whose sum is σ = 21680498. Its totient is φ = 21680496.

The previous prime is 21680479. The next prime is 21680587. The reversal of 21680497 is 79408612.

Together with previous prime (21680479) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17901361 + 3779136 = 4231^2 + 1944^2 .

It is a cyclic number.

It is not a de Polignac number, because 21680497 - 2¹⁵ = 21647729 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21689497) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10840248 + 10840249.

It is an arithmetic number, because the mean of its divisors is an integer number (10840249).

Almost surely, 2^21680497 is an apocalyptic number.

It is an amenable number.

21680497 is a deficient number, since it is larger than the sum of its proper divisors (1).

21680497 is an equidigital number, since it uses as much as digits as its factorization.

21680497 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 24192, while the sum is 37.

The square root of 21680497 is about 4656.2320603681. The cubic root of 21680497 is about 278.8408585285.

The spelling of 21680497 in words is "twenty-one million, six hundred eighty thousand, four hundred ninety-seven".