81640711 has 4 divisors (see below), whose sum is σ = 81688432. Its totient is φ = 81592992.

The previous prime is 81640667. The next prime is 81640721. The reversal of 81640711 is 11704618.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 81640711 - 2⁷ = 81640583 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 81640711.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81640721) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 21195 + ... + 24748.

It is an arithmetic number, because the mean of its divisors is an integer number (20422108).

Almost surely, 2^81640711 is an apocalyptic number.

81640711 is a deficient number, since it is larger than the sum of its proper divisors (47721).

81640711 is a wasteful number, since it uses less digits than its factorization.

81640711 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 47720.

The product of its (nonzero) digits is 1344, while the sum is 28.

The square root of 81640711 is about 9035.5249432449. The cubic root of 81640711 is about 433.8126974621.

The spelling of 81640711 in words is "eighty-one million, six hundred forty thousand, seven hundred eleven".