30981721 has 2 divisors, whose sum is σ = 30981722. Its totient is φ = 30981720.

The previous prime is 30981707. The next prime is 30981737. The reversal of 30981721 is 12718903.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 30913600 + 68121 = 5560^2 + 261^2 .

It is a cyclic number.

It is not a de Polignac number, because 30981721 - 2⁵ = 30981689 is a prime.

It is a super-2 number, since 2×30981721² = 1919734072243682, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (30981791) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15490860 + 15490861.

It is an arithmetic number, because the mean of its divisors is an integer number (15490861).

Almost surely, 2^30981721 is an apocalyptic number.

It is an amenable number.

30981721 is a deficient number, since it is larger than the sum of its proper divisors (1).

30981721 is an equidigital number, since it uses as much as digits as its factorization.

30981721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3024, while the sum is 31.

The square root of 30981721 is about 5566.1226181248. The cubic root of 30981721 is about 314.0763097696.

The spelling of 30981721 in words is "thirty million, nine hundred eighty-one thousand, seven hundred twenty-one".