21017279 has 2 divisors, whose sum is σ = 21017280. Its totient is φ = 21017278.

The previous prime is 21017273. The next prime is 21017303. The reversal of 21017279 is 97271012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21017279 - 2²⁴ = 4240063 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21017273) 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, 10508639 + 10508640.

It is an arithmetic number, because the mean of its divisors is an integer number (10508640).

Almost surely, 2^21017279 is an apocalyptic number.

21017279 is a deficient number, since it is larger than the sum of its proper divisors (1).

21017279 is an equidigital number, since it uses as much as digits as its factorization.

21017279 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1764, while the sum is 29.

The square root of 21017279 is about 4584.4606007686. The cubic root of 21017279 is about 275.9680658635.

The spelling of 21017279 in words is "twenty-one million, seventeen thousand, two hundred seventy-nine".