61640681 has 2 divisors, whose sum is σ = 61640682. Its totient is φ = 61640680.

The previous prime is 61640669. The next prime is 61640707. The reversal of 61640681 is 18604616.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 41165056 + 20475625 = 6416^2 + 4525^2 .

It is a cyclic number.

It is not a de Polignac number, because 61640681 - 2¹⁰ = 61639657 is a prime.

It is a super-2 number, since 2×61640681² = 7599147108287522, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (61640651) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 30820340 + 30820341.

It is an arithmetic number, because the mean of its divisors is an integer number (30820341).

Almost surely, 2^61640681 is an apocalyptic number.

It is an amenable number.

61640681 is a deficient number, since it is larger than the sum of its proper divisors (1).

61640681 is an equidigital number, since it uses as much as digits as its factorization.

61640681 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 6912, while the sum is 32.

The square root of 61640681 is about 7851.1579400748. The cubic root of 61640681 is about 395.0230846948.

The spelling of 61640681 in words is "sixty-one million, six hundred forty thousand, six hundred eighty-one".