820657287491 has 2 divisors, whose sum is σ = 820657287492. Its totient is φ = 820657287490.

The previous prime is 820657287487. The next prime is 820657287529. The reversal of 820657287491 is 194782756028.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 820657287491 - 2² = 820657287487 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 820657287491.

It is not a weakly prime, because it can be changed into another prime (820657287431) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 410328643745 + 410328643746.

It is an arithmetic number, because the mean of its divisors is an integer number (410328643746).

Almost surely, 2^820657287491 is an apocalyptic number.

820657287491 is a deficient number, since it is larger than the sum of its proper divisors (1).

820657287491 is an equidigital number, since it uses as much as digits as its factorization.

820657287491 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 13547520, while the sum is 59.

The spelling of 820657287491 in words is "eight hundred twenty billion, six hundred fifty-seven million, two hundred eighty-seven thousand, four hundred ninety-one".