21829979 has 2 divisors, whose sum is σ = 21829980. Its totient is φ = 21829978.

The previous prime is 21829961. The next prime is 21829981. The reversal of 21829979 is 97992812.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21829979 - 2⁸ = 21829723 is a prime.

Together with 21829981, 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 (21829279) 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, 10914989 + 10914990.

It is an arithmetic number, because the mean of its divisors is an integer number (10914990).

Almost surely, 2^21829979 is an apocalyptic number.

21829979 is a deficient number, since it is larger than the sum of its proper divisors (1).

21829979 is an equidigital number, since it uses as much as digits as its factorization.

21829979 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 163296, while the sum is 47.

The square root of 21829979 is about 4672.2563071818. The cubic root of 21829979 is about 279.4802390015.

The spelling of 21829979 in words is "twenty-one million, eight hundred twenty-nine thousand, nine hundred seventy-nine".