21677809 has 2 divisors, whose sum is σ = 21677810. Its totient is φ = 21677808.

The previous prime is 21677779. The next prime is 21677813. The reversal of 21677809 is 90877612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15626209 + 6051600 = 3953^2 + 2460^2 .

It is a cyclic number.

It is not a de Polignac number, because 21677809 - 2⁷ = 21677681 is a prime.

It is not a weakly prime, because it can be changed into another prime (21677849) 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, 10838904 + 10838905.

It is an arithmetic number, because the mean of its divisors is an integer number (10838905).

Almost surely, 2^21677809 is an apocalyptic number.

It is an amenable number.

21677809 is a deficient number, since it is larger than the sum of its proper divisors (1).

21677809 is an equidigital number, since it uses as much as digits as its factorization.

21677809 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 42336, while the sum is 40.

The square root of 21677809 is about 4655.9434060134. The cubic root of 21677809 is about 278.8293342662.

The spelling of 21677809 in words is "twenty-one million, six hundred seventy-seven thousand, eight hundred nine".