71665781 has 12 divisors (see below), whose sum is σ = 80367840. Its totient is φ = 63376560.

The previous prime is 71665747. The next prime is 71665787. The reversal of 71665781 is 18756617.

It is not a de Polignac number, because 71665781 - 2¹⁴ = 71649397 is a prime.

It is a super-2 number, since 2×71665781² = 10271968332679922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (71665787) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 12680 + ... + 17438.

It is an arithmetic number, because the mean of its divisors is an integer number (6697320).

Almost surely, 2^71665781 is an apocalyptic number.

It is an amenable number.

71665781 is a deficient number, since it is larger than the sum of its proper divisors (8702059).

71665781 is a wasteful number, since it uses less digits than its factorization.

71665781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4844 (or 4807 counting only the distinct ones).

The product of its digits is 70560, while the sum is 41.

The square root of 71665781 is about 8465.5644230022. The cubic root of 71665781 is about 415.3720590424.

The spelling of 71665781 in words is "seventy-one million, six hundred sixty-five thousand, seven hundred eighty-one".