6517981 has 2 divisors, whose sum is σ = 6517982. Its totient is φ = 6517980.

The previous prime is 6517963. The next prime is 6517997. The reversal of 6517981 is 1897156.

6517981 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 can be written as a sum of positive squares in only one way, i.e., 4995225 + 1522756 = 2235^2 + 1234^2 .

It is a cyclic number.

It is not a de Polignac number, because 6517981 - 2⁷ = 6517853 is a prime.

It is a super-2 number, since 2×6517981² = 84968152632722, which contains 22 as substring.

6517981 is a lucky number.

It is a self number, because there is not a number n which added to its sum of digits gives 6517981.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (6517921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3258990 + 3258991.

It is an arithmetic number, because the mean of its divisors is an integer number (3258991).

Almost surely, 2^6517981 is an apocalyptic number.

It is an amenable number.

6517981 is a deficient number, since it is larger than the sum of its proper divisors (1).

6517981 is an equidigital number, since it uses as much as digits as its factorization.

6517981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 15120, while the sum is 37.

The square root of 6517981 is about 2553.0336856375. The cubic root of 6517981 is about 186.7974873070.

The spelling of 6517981 in words is "six million, five hundred seventeen thousand, nine hundred eighty-one".