21118501 has 2 divisors, whose sum is σ = 21118502. Its totient is φ = 21118500.

The previous prime is 21118441. The next prime is 21118507. The reversal of 21118501 is 10581112.

21118501 = 3249² + 3250².

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., 10562500 + 10556001 = 3250^2 + 3249^2 .

It is a cyclic number.

It is not a de Polignac number, because 21118501 - 2⁷ = 21118373 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21118507) 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, 10559250 + 10559251.

It is an arithmetic number, because the mean of its divisors is an integer number (10559251).

Almost surely, 2^21118501 is an apocalyptic number.

21118501 is the 3250-th centered square number.

It is an amenable number.

21118501 is a deficient number, since it is larger than the sum of its proper divisors (1).

21118501 is an equidigital number, since it uses as much as digits as its factorization.

21118501 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 80, while the sum is 19.

The square root of 21118501 is about 4595.4870253326. The cubic root of 21118501 is about 276.4103894470.

Adding to 21118501 its reverse (10581112), we get a palindrome (31699613).

The spelling of 21118501 in words is "twenty-one million, one hundred eighteen thousand, five hundred one".