21408901 has 2 divisors, whose sum is σ = 21408902. Its totient is φ = 21408900.

The previous prime is 21408851. The next prime is 21408913. The reversal of 21408901 is 10980412.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21399876 + 9025 = 4626^2 + 95^2 .

It is a cyclic number.

It is not a de Polignac number, because 21408901 - 2¹⁵ = 21376133 is a prime.

It is equal to p_1354174 and since 21408901 and 1354174 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 (21408971) 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, 10704450 + 10704451.

It is an arithmetic number, because the mean of its divisors is an integer number (10704451).

Almost surely, 2^21408901 is an apocalyptic number.

It is an amenable number.

21408901 is a deficient number, since it is larger than the sum of its proper divisors (1).

21408901 is an equidigital number, since it uses as much as digits as its factorization.

21408901 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 576, while the sum is 25.

The square root of 21408901 is about 4626.9753619400. The cubic root of 21408901 is about 277.6715969226.

The spelling of 21408901 in words is "twenty-one million, four hundred eight thousand, nine hundred one".