77991122220021 has 64 divisors (see below), whose sum is σ = 117273474240000. Its totient is φ = 51858837261504.

The previous prime is 77991122220019. The next prime is 77991122220041. The reversal of 77991122220021 is 12002222119977.

It is not a de Polignac number, because 77991122220021 - 2¹ = 77991122220019 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (77991122220041) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 1431816975 + ... + 1431871443.

It is an arithmetic number, because the mean of its divisors is an integer number (1832398035000).

Almost surely, 2^{77991122220021} is an apocalyptic number.

It is an amenable number.

77991122220021 is a deficient number, since it is larger than the sum of its proper divisors (39282352019979).

77991122220021 is an equidigital number, since it uses as much as digits as its factorization.

77991122220021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 56182 (or 56164 counting only the distinct ones).

The product of its (nonzero) digits is 127008, while the sum is 45.

Adding to 77991122220021 its reverse (12002222119977), we get a palindrome (89993344339998).

The spelling of 77991122220021 in words is "seventy-seven trillion, nine hundred ninety-one billion, one hundred twenty-two million, two hundred twenty thousand, twenty-one".