30721213 has 2 divisors, whose sum is σ = 30721214. Its totient is φ = 30721212.

The previous prime is 30721199. The next prime is 30721231. The reversal of 30721213 is 31212703.

Together with next prime (30721231) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 22638564 + 8082649 = 4758^2 + 2843^2 .

It is an emirp because it is prime and its reverse (31212703) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 30721213 - 2⁵ = 30721181 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (30721253) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15360606 + 15360607.

It is an arithmetic number, because the mean of its divisors is an integer number (15360607).

Almost surely, 2^30721213 is an apocalyptic number.

It is an amenable number.

30721213 is a deficient number, since it is larger than the sum of its proper divisors (1).

30721213 is an equidigital number, since it uses as much as digits as its factorization.

30721213 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 252, while the sum is 19.

The square root of 30721213 is about 5542.6720090584. The cubic root of 30721213 is about 313.1935334046.

Adding to 30721213 its reverse (31212703), we get a palindrome (61933916).

The spelling of 30721213 in words is "thirty million, seven hundred twenty-one thousand, two hundred thirteen".