20631561115391 has 2 divisors, whose sum is σ = 20631561115392. Its totient is φ = 20631561115390.

The previous prime is 20631561115307. The next prime is 20631561115427. The reversal of 20631561115391 is 19351116513602.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20631561115391 is a prime.

It is a super-2 number, since 2×20631561115391² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20631561115591) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10315780557695 + 10315780557696.

It is an arithmetic number, because the mean of its divisors is an integer number (10315780557696).

Almost surely, 2^{20631561115391} is an apocalyptic number.

20631561115391 is a deficient number, since it is larger than the sum of its proper divisors (1).

20631561115391 is an equidigital number, since it uses as much as digits as its factorization.

20631561115391 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 145800, while the sum is 44.

Adding to 20631561115391 its reverse (19351116513602), we get a palindrome (39982677628993).

The spelling of 20631561115391 in words is "twenty trillion, six hundred thirty-one billion, five hundred sixty-one million, one hundred fifteen thousand, three hundred ninety-one".