21615844949 has 2 divisors, whose sum is σ = 21615844950. Its totient is φ = 21615844948.

The previous prime is 21615844907. The next prime is 21615845029. The reversal of 21615844949 is 94944851612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21453460900 + 162384049 = 146470^2 + 12743^2 .

It is a cyclic number.

It is not a de Polignac number, because 21615844949 - 2²⁴ = 21599067733 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21615844949.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21615840949) 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, 10807922474 + 10807922475.

It is an arithmetic number, because the mean of its divisors is an integer number (10807922475).

Almost surely, 2^21615844949 is an apocalyptic number.

It is an amenable number.

21615844949 is a deficient number, since it is larger than the sum of its proper divisors (1).

21615844949 is an equidigital number, since it uses as much as digits as its factorization.

21615844949 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2488320, while the sum is 53.

The spelling of 21615844949 in words is "twenty-one billion, six hundred fifteen million, eight hundred forty-four thousand, nine hundred forty-nine".