61680781 has 2 divisors, whose sum is σ = 61680782. Its totient is φ = 61680780.

The previous prime is 61680761. The next prime is 61680797. The reversal of 61680781 is 18708616.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 34327881 + 27352900 = 5859^2 + 5230^2 .

It is a cyclic number.

It is not a de Polignac number, because 61680781 - 2⁷ = 61680653 is a prime.

It is a super-2 number, since 2×61680781² = 7609037489539922, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 61680781.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (61680761) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 30840390 + 30840391.

It is an arithmetic number, because the mean of its divisors is an integer number (30840391).

Almost surely, 2^61680781 is an apocalyptic number.

It is an amenable number.

61680781 is a deficient number, since it is larger than the sum of its proper divisors (1).

61680781 is an equidigital number, since it uses as much as digits as its factorization.

61680781 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 16128, while the sum is 37.

The square root of 61680781 is about 7853.7112883019. The cubic root of 61680781 is about 395.1087261451.

The spelling of 61680781 in words is "sixty-one million, six hundred eighty thousand, seven hundred eighty-one".