20312981891 has 2 divisors, whose sum is σ = 20312981892. Its totient is φ = 20312981890.

The previous prime is 20312981881. The next prime is 20312981893. The reversal of 20312981891 is 19818921302.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20312981891 - 2⁶ = 20312981827 is a prime.

Together with 20312981893, 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 (20312981893) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10156490945 + 10156490946.

It is an arithmetic number, because the mean of its divisors is an integer number (10156490946).

Almost surely, 2^20312981891 is an apocalyptic number.

20312981891 is a deficient number, since it is larger than the sum of its proper divisors (1).

20312981891 is an equidigital number, since it uses as much as digits as its factorization.

20312981891 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 62208, while the sum is 44.

The spelling of 20312981891 in words is "twenty billion, three hundred twelve million, nine hundred eighty-one thousand, eight hundred ninety-one".