61666681 has 2 divisors, whose sum is σ = 61666682. Its totient is φ = 61666680.

The previous prime is 61666651. The next prime is 61666691. The reversal of 61666681 is 18666616.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 39576681 + 22090000 = 6291^2 + 4700^2 .It is also a bemirp because it and its reverse can be mirrored producing other two distinct primes, 18999919 and 91999981.

It is a cyclic number.

It is not a de Polignac number, because 61666681 - 2¹⁷ = 61535609 is a prime.

It is a super-2 number, since 2×61666681² = 7605559091111522, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (61666651) 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, 30833340 + 30833341.

It is an arithmetic number, because the mean of its divisors is an integer number (30833341).

Almost surely, 2^61666681 is an apocalyptic number.

It is an amenable number.

61666681 is a deficient number, since it is larger than the sum of its proper divisors (1).

61666681 is an equidigital number, since it uses as much as digits as its factorization.

61666681 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 62208, while the sum is 40.

The square root of 61666681 is about 7852.8135722173. The cubic root of 61666681 is about 395.0786170495.

The spelling of 61666681 in words is "sixty-one million, six hundred sixty-six thousand, six hundred eighty-one".