20408661491 has 2 divisors, whose sum is σ = 20408661492. Its totient is φ = 20408661490.

The previous prime is 20408661487. The next prime is 20408661509. The reversal of 20408661491 is 19416680402.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 20408661491 - 2² = 20408661487 is a prime.

It is not a weakly prime, because it can be changed into another prime (20408661191) 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, 10204330745 + 10204330746.

It is an arithmetic number, because the mean of its divisors is an integer number (10204330746).

Almost surely, 2^20408661491 is an apocalyptic number.

20408661491 is a deficient number, since it is larger than the sum of its proper divisors (1).

20408661491 is an equidigital number, since it uses as much as digits as its factorization.

20408661491 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 82944, while the sum is 41.

The spelling of 20408661491 in words is "twenty billion, four hundred eight million, six hundred sixty-one thousand, four hundred ninety-one".