21015505249 has 2 divisors, whose sum is σ = 21015505250. Its totient is φ = 21015505248.

The previous prime is 21015505241. The next prime is 21015505253. The reversal of 21015505249 is 94250551012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20547215649 + 468289600 = 143343^2 + 21640^2 .

It is a cyclic number.

It is not a de Polignac number, because 21015505249 - 2³ = 21015505241 is a prime.

It is not a weakly prime, because it can be changed into another prime (21015505241) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10507752624 + 10507752625.

It is an arithmetic number, because the mean of its divisors is an integer number (10507752625).

Almost surely, 2^21015505249 is an apocalyptic number.

It is an amenable number.

21015505249 is a deficient number, since it is larger than the sum of its proper divisors (1).

21015505249 is an equidigital number, since it uses as much as digits as its factorization.

21015505249 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 18000, while the sum is 34.

The spelling of 21015505249 in words is "twenty-one billion, fifteen million, five hundred five thousand, two hundred forty-nine".