81723155 has 4 divisors (see below), whose sum is σ = 98067792. Its totient is φ = 65378520.

The previous prime is 81723151. The next prime is 81723157. The reversal of 81723155 is 55132718.

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

It is not a de Polignac number, because 81723155 - 2² = 81723151 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81723151) 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, 8172311 + ... + 8172320.

It is an arithmetic number, because the mean of its divisors is an integer number (24516948).

Almost surely, 2^81723155 is an apocalyptic number.

81723155 is a deficient number, since it is larger than the sum of its proper divisors (16344637).

81723155 is a wasteful number, since it uses less digits than its factorization.

81723155 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16344636.

The product of its digits is 8400, while the sum is 32.

The square root of 81723155 is about 9040.0860062280. The cubic root of 81723155 is about 433.9586753747.

The spelling of 81723155 in words is "eighty-one million, seven hundred twenty-three thousand, one hundred fifty-five".