21102979 has 2 divisors, whose sum is σ = 21102980. Its totient is φ = 21102978.

The previous prime is 21102947. The next prime is 21103003. The reversal of 21102979 is 97920112.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21102979 - 2⁵ = 21102947 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21102979.

It is not a weakly prime, because it can be changed into another prime (21102919) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10551489 + 10551490.

It is an arithmetic number, because the mean of its divisors is an integer number (10551490).

Almost surely, 2^21102979 is an apocalyptic number.

21102979 is a deficient number, since it is larger than the sum of its proper divisors (1).

21102979 is an equidigital number, since it uses as much as digits as its factorization.

21102979 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2268, while the sum is 31.

The square root of 21102979 is about 4593.7978841042. The cubic root of 21102979 is about 276.3426527320.

The spelling of 21102979 in words is "twenty-one million, one hundred two thousand, nine hundred seventy-nine".