30531721921 has 2 divisors, whose sum is σ = 30531721922. Its totient is φ = 30531721920.

The previous prime is 30531721879. The next prime is 30531721939. The reversal of 30531721921 is 12912713503.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 26818647696 + 3713074225 = 163764^2 + 60935^2 .

It is an emirp because it is prime and its reverse (12912713503) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-30531721921 is a prime.

It is a super-2 number, since 2×30531721921² (a number of 22 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (30531721951) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15265860960 + 15265860961.

It is an arithmetic number, because the mean of its divisors is an integer number (15265860961).

Almost surely, 2^30531721921 is an apocalyptic number.

It is an amenable number.

30531721921 is a deficient number, since it is larger than the sum of its proper divisors (1).

30531721921 is an equidigital number, since it uses as much as digits as its factorization.

30531721921 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 11340, while the sum is 34.

The spelling of 30531721921 in words is "thirty billion, five hundred thirty-one million, seven hundred twenty-one thousand, nine hundred twenty-one".