21420023 has 2 divisors, whose sum is σ = 21420024. Its totient is φ = 21420022.

The previous prime is 21420013. The next prime is 21420031. The reversal of 21420023 is 32002412.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21420023 - 2⁸ = 21419767 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21420013) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10710011 + 10710012.

It is an arithmetic number, because the mean of its divisors is an integer number (10710012).

Almost surely, 2^21420023 is an apocalyptic number.

21420023 is a deficient number, since it is larger than the sum of its proper divisors (1).

21420023 is an equidigital number, since it uses as much as digits as its factorization.

21420023 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 96, while the sum is 14.

The square root of 21420023 is about 4628.1770709427. The cubic root of 21420023 is about 277.7196723916.

Adding to 21420023 its reverse (32002412), we get a palindrome (53422435).

The spelling of 21420023 in words is "twenty-one million, four hundred twenty thousand, twenty-three".