20502791891 has 2 divisors, whose sum is σ = 20502791892. Its totient is φ = 20502791890.

The previous prime is 20502791857. The next prime is 20502791893. The reversal of 20502791891 is 19819720502.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20502791891 - 2²⁶ = 20435683027 is a prime.

Together with 20502791893, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (20502791893) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10251395945 + 10251395946.

It is an arithmetic number, because the mean of its divisors is an integer number (10251395946).

Almost surely, 2^20502791891 is an apocalyptic number.

20502791891 is a deficient number, since it is larger than the sum of its proper divisors (1).

20502791891 is an equidigital number, since it uses as much as digits as its factorization.

20502791891 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 90720, while the sum is 44.

The spelling of 20502791891 in words is "twenty billion, five hundred two million, seven hundred ninety-one thousand, eight hundred ninety-one".