21418513 has 2 divisors, whose sum is σ = 21418514. Its totient is φ = 21418512.

The previous prime is 21418477. The next prime is 21418531. The reversal of 21418513 is 31581412.

21418513 = 3272² + 3273².

Together with next prime (21418531) it forms an Ormiston pair, because they use the same digits, order apart.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10712529 + 10705984 = 3273^2 + 3272^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21418513 is a prime.

It is not a weakly prime, because it can be changed into another prime (21418013) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10709256 + 10709257.

It is an arithmetic number, because the mean of its divisors is an integer number (10709257).

Almost surely, 2^21418513 is an apocalyptic number.

21418513 is the 3273-rd centered square number.

It is an amenable number.

21418513 is a deficient number, since it is larger than the sum of its proper divisors (1).

21418513 is an equidigital number, since it uses as much as digits as its factorization.

21418513 is an evil number, because the sum of its binary digits is even.

The product of its digits is 960, while the sum is 25.

The square root of 21418513 is about 4628.0139368848. The cubic root of 21418513 is about 277.7131463083.

Adding to 21418513 its reverse (31581412), we get a palindrome (52999925).

The spelling of 21418513 in words is "twenty-one million, four hundred eighteen thousand, five hundred thirteen".