21030979 has 2 divisors, whose sum is σ = 21030980. Its totient is φ = 21030978.

The previous prime is 21030973. The next prime is 21031009. The reversal of 21030979 is 97903012.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21030979 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21030979.

It is not a weakly prime, because it can be changed into another prime (21030973) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10515489 + 10515490.

It is an arithmetic number, because the mean of its divisors is an integer number (10515490).

Almost surely, 2^21030979 is an apocalyptic number.

21030979 is a deficient number, since it is larger than the sum of its proper divisors (1).

21030979 is an equidigital number, since it uses as much as digits as its factorization.

21030979 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3402, while the sum is 31.

The square root of 21030979 is about 4585.9545353176. The cubic root of 21030979 is about 276.0280156047.

The spelling of 21030979 in words is "twenty-one million, thirty thousand, nine hundred seventy-nine".