661972681 has 2 divisors, whose sum is σ = 661972682. Its totient is φ = 661972680.

The previous prime is 661972669. The next prime is 661972693. The reversal of 661972681 is 186279166.

It is a balanced prime because it is at equal distance from previous prime (661972669) and next prime (661972693).

It can be written as a sum of positive squares in only one way, i.e., 605947456 + 56025225 = 24616^2 + 7485^2 .

It is a cyclic number.

It is not a de Polignac number, because 661972681 - 2⁹ = 661972169 is a prime.

It is a super-2 number, since 2×661972681² = 876415660780655522, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (661972981) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330986340 + 330986341.

It is an arithmetic number, because the mean of its divisors is an integer number (330986341).

Almost surely, 2^661972681 is an apocalyptic number.

It is an amenable number.

661972681 is a deficient number, since it is larger than the sum of its proper divisors (1).

661972681 is an equidigital number, since it uses as much as digits as its factorization.

661972681 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 217728, while the sum is 46.

The square root of 661972681 is about 25728.8297635163. The cubic root of 661972681 is about 871.5253467254.

The spelling of 661972681 in words is "six hundred sixty-one million, nine hundred seventy-two thousand, six hundred eighty-one".