21403979 has 2 divisors, whose sum is σ = 21403980. Its totient is φ = 21403978.

The previous prime is 21403973. The next prime is 21404017. The reversal of 21403979 is 97930412.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21403979 is a prime.

It is equal to p_1353887 and since 21403979 and 1353887 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (21403973) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10701989 + 10701990.

It is an arithmetic number, because the mean of its divisors is an integer number (10701990).

Almost surely, 2^21403979 is an apocalyptic number.

21403979 is a deficient number, since it is larger than the sum of its proper divisors (1).

21403979 is an equidigital number, since it uses as much as digits as its factorization.

21403979 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 13608, while the sum is 35.

The square root of 21403979 is about 4626.4434504271. The cubic root of 21403979 is about 277.6503159867.

The spelling of 21403979 in words is "twenty-one million, four hundred three thousand, nine hundred seventy-nine".