9819721931 has 2 divisors, whose sum is σ = 9819721932. Its totient is φ = 9819721930.

The previous prime is 9819721909. The next prime is 9819721943. The reversal of 9819721931 is 1391279189.

9819721931 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-9819721931 is a prime.

It is a super-2 number, since 2×9819721931² (a number of 21 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 9819721931.

It is not a weakly prime, because it can be changed into another prime (9819721981) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4909860965 + 4909860966.

It is an arithmetic number, because the mean of its divisors is an integer number (4909860966).

Almost surely, 2^9819721931 is an apocalyptic number.

9819721931 is a deficient number, since it is larger than the sum of its proper divisors (1).

9819721931 is an equidigital number, since it uses as much as digits as its factorization.

9819721931 is an evil number, because the sum of its binary digits is even.

The product of its digits is 244944, while the sum is 50.

The square root of 9819721931 is about 99094.5100951612. The cubic root of 9819721931 is about 2141.4095243549.

The spelling of 9819721931 in words is "nine billion, eight hundred nineteen million, seven hundred twenty-one thousand, nine hundred thirty-one".