81656671 has 2 divisors, whose sum is σ = 81656672. Its totient is φ = 81656670.

The previous prime is 81656657. The next prime is 81656677. The reversal of 81656671 is 17665618.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81656671 - 2¹⁵ = 81623903 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81656677) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40828335 + 40828336.

It is an arithmetic number, because the mean of its divisors is an integer number (40828336).

Almost surely, 2^81656671 is an apocalyptic number.

81656671 is a deficient number, since it is larger than the sum of its proper divisors (1).

81656671 is an equidigital number, since it uses as much as digits as its factorization.

81656671 is an evil number, because the sum of its binary digits is even.

The product of its digits is 60480, while the sum is 40.

The square root of 81656671 is about 9036.4080806480. The cubic root of 81656671 is about 433.8409644033.

The spelling of 81656671 in words is "eighty-one million, six hundred fifty-six thousand, six hundred seventy-one".