21018461 has 2 divisors, whose sum is σ = 21018462. Its totient is φ = 21018460.

The previous prime is 21018407. The next prime is 21018467. The reversal of 21018461 is 16481012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18232900 + 2785561 = 4270^2 + 1669^2 .

It is a cyclic number.

It is not a de Polignac number, because 21018461 - 2⁶ = 21018397 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21018467) 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, 10509230 + 10509231.

It is an arithmetic number, because the mean of its divisors is an integer number (10509231).

Almost surely, 2^21018461 is an apocalyptic number.

It is an amenable number.

21018461 is a deficient number, since it is larger than the sum of its proper divisors (1).

21018461 is an equidigital number, since it uses as much as digits as its factorization.

21018461 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 384, while the sum is 23.

The square root of 21018461 is about 4584.5895127045. The cubic root of 21018461 is about 275.9732391963.

Adding to 21018461 its reverse (16481012), we get a palindrome (37499473).

The spelling of 21018461 in words is "twenty-one million, eighteen thousand, four hundred sixty-one".