21125501 has 2 divisors, whose sum is σ = 21125502. Its totient is φ = 21125500.

The previous prime is 21125491. The next prime is 21125521. The reversal of 21125501 is 10552112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16605625 + 4519876 = 4075^2 + 2126^2 .

It is a cyclic number.

It is not a de Polignac number, because 21125501 - 2¹⁴ = 21109117 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21125501.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21125521) 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, 10562750 + 10562751.

It is an arithmetic number, because the mean of its divisors is an integer number (10562751).

Almost surely, 2^21125501 is an apocalyptic number.

It is an amenable number.

21125501 is a deficient number, since it is larger than the sum of its proper divisors (1).

21125501 is an equidigital number, since it uses as much as digits as its factorization.

21125501 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 100, while the sum is 17.

The square root of 21125501 is about 4596.2485790044. The cubic root of 21125501 is about 276.4409260049.

Adding to 21125501 its reverse (10552112), we get a palindrome (31677613).

The spelling of 21125501 in words is "twenty-one million, one hundred twenty-five thousand, five hundred one".