21915779 has 2 divisors, whose sum is σ = 21915780. Its totient is φ = 21915778.

The previous prime is 21915769. The next prime is 21915781. The reversal of 21915779 is 97751912.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21915779 - 2⁴ = 21915763 is a prime.

Together with 21915781, 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 (21915739) 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, 10957889 + 10957890.

It is an arithmetic number, because the mean of its divisors is an integer number (10957890).

Almost surely, 2^21915779 is an apocalyptic number.

21915779 is a deficient number, since it is larger than the sum of its proper divisors (1).

21915779 is an equidigital number, since it uses as much as digits as its factorization.

21915779 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 39690, while the sum is 41.

The square root of 21915779 is about 4681.4291621256. The cubic root of 21915779 is about 279.8459143710.

The spelling of 21915779 in words is "twenty-one million, nine hundred fifteen thousand, seven hundred seventy-nine".