31111020821 has 2 divisors, whose sum is σ = 31111020822. Its totient is φ = 31111020820.

The previous prime is 31111020803. The next prime is 31111020823. The reversal of 31111020821 is 12802011113.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 27220380196 + 3890640625 = 164986^2 + 62375^2 .

It is an emirp because it is prime and its reverse (12802011113) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 31111020821 - 2⁶ = 31111020757 is a prime.

Together with 31111020823, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 31111020793 and 31111020802.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31111020823) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15555510410 + 15555510411.

It is an arithmetic number, because the mean of its divisors is an integer number (15555510411).

Almost surely, 2^31111020821 is an apocalyptic number.

It is an amenable number.

31111020821 is a deficient number, since it is larger than the sum of its proper divisors (1).

31111020821 is an equidigital number, since it uses as much as digits as its factorization.

31111020821 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 96, while the sum is 20.

Adding to 31111020821 its reverse (12802011113), we get a palindrome (43913031934).

The spelling of 31111020821 in words is "thirty-one billion, one hundred eleven million, twenty thousand, eight hundred twenty-one".