81718951 has 4 divisors (see below), whose sum is σ = 83260872. Its totient is φ = 80177032.

The previous prime is 81718939. The next prime is 81718961. The reversal of 81718951 is 15981718.

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 81718951 - 2¹⁵ = 81686183 is a prime.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81718961) 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, 770881 + ... + 770986.

It is an arithmetic number, because the mean of its divisors is an integer number (20815218).

Almost surely, 2^81718951 is an apocalyptic number.

81718951 is a deficient number, since it is larger than the sum of its proper divisors (1541921).

81718951 is a wasteful number, since it uses less digits than its factorization.

81718951 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1541920.

The product of its digits is 20160, while the sum is 40.

The square root of 81718951 is about 9039.8534833259. The cubic root of 81718951 is about 433.9512340175.

The spelling of 81718951 in words is "eighty-one million, seven hundred eighteen thousand, nine hundred fifty-one".