21391301 has 2 divisors, whose sum is σ = 21391302. Its totient is φ = 21391300.

The previous prime is 21391267. The next prime is 21391303. The reversal of 21391301 is 10319312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21390625 + 676 = 4625^2 + 26^2 .

It is a cyclic number.

It is not a de Polignac number, because 21391301 - 2²² = 17196997 is a prime.

It is a Sophie Germain prime.

Together with 21391303, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is equal to p_1353143 and since 21391301 and 1353143 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21391303) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10695650 + 10695651.

It is an arithmetic number, because the mean of its divisors is an integer number (10695651).

Almost surely, 2^21391301 is an apocalyptic number.

It is an amenable number.

21391301 is a deficient number, since it is larger than the sum of its proper divisors (1).

21391301 is an equidigital number, since it uses as much as digits as its factorization.

21391301 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 162, while the sum is 20.

The square root of 21391301 is about 4625.0730805037. The cubic root of 21391301 is about 277.5954859022.

The spelling of 21391301 in words is "twenty-one million, three hundred ninety-one thousand, three hundred one".