21678697 has 2 divisors, whose sum is σ = 21678698. Its totient is φ = 21678696.

The previous prime is 21678667. The next prime is 21678731. The reversal of 21678697 is 79687612.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21678336 + 361 = 4656^2 + 19^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21678697 is a prime.

It is not a weakly prime, because it can be changed into another prime (21678667) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10839348 + 10839349.

It is an arithmetic number, because the mean of its divisors is an integer number (10839349).

Almost surely, 2^21678697 is an apocalyptic number.

It is an amenable number.

21678697 is a deficient number, since it is larger than the sum of its proper divisors (1).

21678697 is an equidigital number, since it uses as much as digits as its factorization.

21678697 is an evil number, because the sum of its binary digits is even.

The product of its digits is 254016, while the sum is 46.

The square root of 21678697 is about 4656.0387670207. The cubic root of 21678697 is about 278.8331414939.

The spelling of 21678697 in words is "twenty-one million, six hundred seventy-eight thousand, six hundred ninety-seven".