71385781 has 2 divisors, whose sum is σ = 71385782. Its totient is φ = 71385780.

The previous prime is 71385773. The next prime is 71385817. The reversal of 71385781 is 18758317.

It is a happy number.

Together with next prime (71385817) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 69872881 + 1512900 = 8359^2 + 1230^2 .

It is a cyclic number.

It is not a de Polignac number, because 71385781 - 2³ = 71385773 is a prime.

It is a super-2 number, since 2×71385781² = 10191859457959922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (71385701) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 35692890 + 35692891.

It is an arithmetic number, because the mean of its divisors is an integer number (35692891).

Almost surely, 2^71385781 is an apocalyptic number.

It is an amenable number.

71385781 is a deficient number, since it is larger than the sum of its proper divisors (1).

71385781 is an equidigital number, since it uses as much as digits as its factorization.

71385781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 47040, while the sum is 40.

The square root of 71385781 is about 8449.0106521415. The cubic root of 71385781 is about 414.8303966557.

The spelling of 71385781 in words is "seventy-one million, three hundred eighty-five thousand, seven hundred eighty-one".