21678277 has 2 divisors, whose sum is σ = 21678278. Its totient is φ = 21678276.

The previous prime is 21678257. The next prime is 21678313. The reversal of 21678277 is 77287612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20848356 + 829921 = 4566^2 + 911^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21678277 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21678257) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10839138 + 10839139.

It is an arithmetic number, because the mean of its divisors is an integer number (10839139).

Almost surely, 2^21678277 is an apocalyptic number.

It is an amenable number.

21678277 is a deficient number, since it is larger than the sum of its proper divisors (1).

21678277 is an equidigital number, since it uses as much as digits as its factorization.

21678277 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 65856, while the sum is 40.

The square root of 21678277 is about 4655.9936640850. The cubic root of 21678277 is about 278.8313407911.

The spelling of 21678277 in words is "twenty-one million, six hundred seventy-eight thousand, two hundred seventy-seven".