61855681 has 2 divisors, whose sum is σ = 61855682. Its totient is φ = 61855680.

The previous prime is 61855679. The next prime is 61855691. The reversal of 61855681 is 18655816.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 61074225 + 781456 = 7815^2 + 884^2 .

It is a cyclic number.

It is not a de Polignac number, because 61855681 - 2¹ = 61855679 is a prime.

It is a super-2 number, since 2×61855681² = 7652250543947522, which contains 22 as substring.

Together with 61855679, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (61855691) 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, 30927840 + 30927841.

It is an arithmetic number, because the mean of its divisors is an integer number (30927841).

Almost surely, 2^61855681 is an apocalyptic number.

It is an amenable number.

61855681 is a deficient number, since it is larger than the sum of its proper divisors (1).

61855681 is an equidigital number, since it uses as much as digits as its factorization.

61855681 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 57600, while the sum is 40.

The square root of 61855681 is about 7864.8382691572. The cubic root of 61855681 is about 395.4818261662.

The spelling of 61855681 in words is "sixty-one million, eight hundred fifty-five thousand, six hundred eighty-one".