21707977 has 2 divisors, whose sum is σ = 21707978. Its totient is φ = 21707976.

The previous prime is 21707969. The next prime is 21707981. The reversal of 21707977 is 77970712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21631801 + 76176 = 4651^2 + 276^2 .

It is a cyclic number.

It is not a de Polignac number, because 21707977 - 2³ = 21707969 is a prime.

It is not a weakly prime, because it can be changed into another prime (21707927) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10853988 + 10853989.

It is an arithmetic number, because the mean of its divisors is an integer number (10853989).

Almost surely, 2^21707977 is an apocalyptic number.

It is an amenable number.

21707977 is a deficient number, since it is larger than the sum of its proper divisors (1).

21707977 is an equidigital number, since it uses as much as digits as its factorization.

21707977 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 43218, while the sum is 40.

The square root of 21707977 is about 4659.1820097524. The cubic root of 21707977 is about 278.9586189232.

It can be divided in two parts, 217079 and 77, that added together give a square (217156 = 466²).

The spelling of 21707977 in words is "twenty-one million, seven hundred seven thousand, nine hundred seventy-seven".