20840991979 has 2 divisors, whose sum is σ = 20840991980. Its totient is φ = 20840991978.

The previous prime is 20840991971. The next prime is 20840992009. The reversal of 20840991979 is 97919904802.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 20840991979 - 2³ = 20840991971 is a prime.

It is not a weakly prime, because it can be changed into another prime (20840991971) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10420495989 + 10420495990.

It is an arithmetic number, because the mean of its divisors is an integer number (10420495990).

Almost surely, 2^20840991979 is an apocalyptic number.

20840991979 is a deficient number, since it is larger than the sum of its proper divisors (1).

20840991979 is an equidigital number, since it uses as much as digits as its factorization.

20840991979 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2939328, while the sum is 58.

The spelling of 20840991979 in words is "twenty billion, eight hundred forty million, nine hundred ninety-one thousand, nine hundred seventy-nine".