65909981 has 2 divisors, whose sum is σ = 65909982. Its totient is φ = 65909980.

The previous prime is 65909971. The next prime is 65909989. The reversal of 65909981 is 18990956.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 52330756 + 13579225 = 7234^2 + 3685^2 .

It is a cyclic number.

It is not a de Polignac number, because 65909981 - 2¹⁰ = 65908957 is a prime.

It is a super-2 number, since 2×65909981² = 8688251190840722, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (65909989) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 32954990 + 32954991.

It is an arithmetic number, because the mean of its divisors is an integer number (32954991).

Almost surely, 2^65909981 is an apocalyptic number.

It is an amenable number.

65909981 is a deficient number, since it is larger than the sum of its proper divisors (1).

65909981 is an equidigital number, since it uses as much as digits as its factorization.

65909981 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 174960, while the sum is 47.

The square root of 65909981 is about 8118.4962277506. The cubic root of 65909981 is about 403.9401869591.

The spelling of 65909981 in words is "sixty-five million, nine hundred nine thousand, nine hundred eighty-one".