20605249391 has 2 divisors, whose sum is σ = 20605249392. Its totient is φ = 20605249390.

The previous prime is 20605249387. The next prime is 20605249403. The reversal of 20605249391 is 19394250602.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 20605249391 - 2² = 20605249387 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20605249351) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10302624695 + 10302624696.

It is an arithmetic number, because the mean of its divisors is an integer number (10302624696).

Almost surely, 2^20605249391 is an apocalyptic number.

20605249391 is a deficient number, since it is larger than the sum of its proper divisors (1).

20605249391 is an equidigital number, since it uses as much as digits as its factorization.

20605249391 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 116640, while the sum is 41.

Adding to 20605249391 its reverse (19394250602), we get a palindrome (39999499993).

The spelling of 20605249391 in words is "twenty billion, six hundred five million, two hundred forty-nine thousand, three hundred ninety-one".