81723515 has 4 divisors (see below), whose sum is σ = 98068224. Its totient is φ = 65378808.

The previous prime is 81723463. The next prime is 81723557. The reversal of 81723515 is 51532718.

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 81723515 - 2²² = 77529211 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8172347 + ... + 8172356.

It is an arithmetic number, because the mean of its divisors is an integer number (24517056).

Almost surely, 2^81723515 is an apocalyptic number.

81723515 is a deficient number, since it is larger than the sum of its proper divisors (16344709).

81723515 is a wasteful number, since it uses less digits than its factorization.

81723515 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16344708.

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

The square root of 81723515 is about 9040.1059175211. The cubic root of 81723515 is about 433.9593125865.

The spelling of 81723515 in words is "eighty-one million, seven hundred twenty-three thousand, five hundred fifteen".