21779579 has 2 divisors, whose sum is σ = 21779580. Its totient is φ = 21779578.

The previous prime is 21779573. The next prime is 21779581. The reversal of 21779579 is 97597712.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21779579 is a prime.

It is a super-2 number, since 2×21779579² = 948700122834482, which contains 22 as substring.

Together with 21779581, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21779573) 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, 10889789 + 10889790.

It is an arithmetic number, because the mean of its divisors is an integer number (10889790).

Almost surely, 2^21779579 is an apocalyptic number.

21779579 is a deficient number, since it is larger than the sum of its proper divisors (1).

21779579 is an equidigital number, since it uses as much as digits as its factorization.

21779579 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 277830, while the sum is 47.

The square root of 21779579 is about 4666.8596507716. The cubic root of 21779579 is about 279.2649897766.

The spelling of 21779579 in words is "twenty-one million, seven hundred seventy-nine thousand, five hundred seventy-nine".