21149539 has 2 divisors, whose sum is σ = 21149540. Its totient is φ = 21149538.

The previous prime is 21149509. The next prime is 21149549. The reversal of 21149539 is 93594112.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21149539 - 2¹⁷ = 21018467 is a prime.

It is not a weakly prime, because it can be changed into another prime (21149509) 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, 10574769 + 10574770.

It is an arithmetic number, because the mean of its divisors is an integer number (10574770).

Almost surely, 2^21149539 is an apocalyptic number.

21149539 is a deficient number, since it is larger than the sum of its proper divisors (1).

21149539 is an equidigital number, since it uses as much as digits as its factorization.

21149539 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 9720, while the sum is 34.

The square root of 21149539 is about 4598.8627942134. The cubic root of 21149539 is about 276.5457372180.

It can be divided in two parts, 21149 and 539, that multiplied together give a palindrome (11399311).

The spelling of 21149539 in words is "twenty-one million, one hundred forty-nine thousand, five hundred thirty-nine".