21242479 has 2 divisors, whose sum is σ = 21242480. Its totient is φ = 21242478.

The previous prime is 21242461. The next prime is 21242491. The reversal of 21242479 is 97424212.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21242479 - 2⁹ = 21241967 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21242479.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21245479) 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, 10621239 + 10621240.

It is an arithmetic number, because the mean of its divisors is an integer number (10621240).

Almost surely, 2^21242479 is an apocalyptic number.

21242479 is a deficient number, since it is larger than the sum of its proper divisors (1).

21242479 is an equidigital number, since it uses as much as digits as its factorization.

21242479 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 8064, while the sum is 31.

The square root of 21242479 is about 4608.9563894661. The cubic root of 21242479 is about 276.9502315153.

The spelling of 21242479 in words is "twenty-one million, two hundred forty-two thousand, four hundred seventy-nine".