81724663 has 4 divisors (see below), whose sum is σ = 81745200. Its totient is φ = 81704128.

The previous prime is 81724637. The next prime is 81724667. The reversal of 81724663 is 36642718.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81724663 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81724667) 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, 2170 + ... + 12967.

It is an arithmetic number, because the mean of its divisors is an integer number (20436300).

Almost surely, 2^81724663 is an apocalyptic number.

81724663 is a deficient number, since it is larger than the sum of its proper divisors (20537).

81724663 is a wasteful number, since it uses less digits than its factorization.

81724663 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20536.

The product of its digits is 48384, while the sum is 37.

The square root of 81724663 is about 9040.1694121294. The cubic root of 81724663 is about 433.9613445719.

The spelling of 81724663 in words is "eighty-one million, seven hundred twenty-four thousand, six hundred sixty-three".