21420073 has 2 divisors, whose sum is σ = 21420074. Its totient is φ = 21420072.

The previous prime is 21420043. The next prime is 21420079. The reversal of 21420073 is 37002412.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18045504 + 3374569 = 4248^2 + 1837^2 .

It is a cyclic number.

It is not a de Polignac number, because 21420073 - 2¹⁷ = 21289001 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21420073.

It is not a weakly prime, because it can be changed into another prime (21420079) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10710036 + 10710037.

It is an arithmetic number, because the mean of its divisors is an integer number (10710037).

Almost surely, 2^21420073 is an apocalyptic number.

It is an amenable number.

21420073 is a deficient number, since it is larger than the sum of its proper divisors (1).

21420073 is an equidigital number, since it uses as much as digits as its factorization.

21420073 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 336, while the sum is 19.

The square root of 21420073 is about 4628.1824726344. The cubic root of 21420073 is about 277.7198884818.

Adding to 21420073 its reverse (37002412), we get a palindrome (58422485).

The spelling of 21420073 in words is "twenty-one million, four hundred twenty thousand, seventy-three".